Dental adhesive

ABSTRACT

The present invention relates to an aqueous dental composition having a pH of at most 7. Furthermore, the present invention relates to the use of a specific composition for the preparation of an aqueous dental composition.

This application is a continuation application of U.S. application Ser.No. 15/747,803, filed Jan. 26, 2018.

FIELD OF THE INVENTION

The present invention relates to an aqueous dental composition having apH of at most 7. Furthermore, the present invention relates to the useof a specific composition for the preparation of an aqueous dentalcomposition. The aqueous dental composition according to the presentinvention may be a one-part dental composition. The aqueous dentalcomposition according to the present invention has improved handlingproperties due to excellent wetting properties, among others due toimproved penetration properties, and shows improved adhesive propertiesto both enamel and dentin. The aqueous dental composition according tothe present invention also has high storage stability and excellentmechanical properties when cured.

BACKGROUND OF THE INVENTION

The restoration of dental structures is typically accomplished by theapplication of a dental adhesive and subsequently a restorative materialto the dental structures. Dental adhesives are also used in the bondingof dental materials such as orthodontic appliances to a dentalstructure. In order to facilitate an intimate interaction between thedental composition and the dental structure, various pretreatmentprocesses are often used in order to improve the bonding of the dentalcomposition to dentin or enamel. A typical pretreatment may includeetching and priming of the dental surface with the aim of fully wettingthe dental structure with the dental composition.

However, given that etchants, primers, and adhesives are typicallyapplied in a step-wise fashion, the restoration of dental structures isoften a complex multistep procedure.

Accordingly, a need exists for simplifying conventional restorative ororthodontic procedures. For example, it would be desirable to provide adental composition that accomplishes an intimate interaction between thedental structure and the dental composition without requiring separateetching and priming steps. A suitable dental composition couldadvantageously be formulated as an aqueous polymerizable dentalcompositions for use as a dental adhesive composition, a dental bondingagent, a pit and fissure sealant, a dental desensitizing composition, apulp capping composition, a dental composite, dental glass ionomercement, a dental cement or a dental root canal sealer composition.Moreover, a generic dental composition may be a dental infiltrant.

WO 2014/040729 A1 and its family member EP 2 705 827 A1 disclose anaqueous dental composition comprising a polymerizable allyl(meth)acrylamide compound preferably having two allyl(meth)acrylamidemoieties, which may be linked via a straight chain or branched chainalkylene group or a cycloalkylene group. The allyl (meth)acrylamidecompound has a favorable polymerization enthalpy and high hydrolysisstability. Dental compositions such as those disclosed in WO 2014/040729A1 and EP 2 705 827 A1 have a viscosity which tends to be high.

EP 1 911 434 A1 discloses a dental composition containing apolymerizable acidic phosphoric acid ester monomer.

SUMMARY OF THE INVENTION

It is the problem of the present invention to provide an aqueous dentalcomposition having a pH of at most 7, which has good wetting propertiesto a dental surface and an advantageous viscosity, whereby said dentalcomposition may be polymerized to provide high adhesion to dentine andenamel, while the aqueous dental composition has high storage stabilityof the uncured dental composition and high stability after curing in themouth of a patient.

The present invention provides an aqueous dental composition having a pHof at most 7, comprising:

-   (a) 1 to 70 percent by weight based on the total weight of the    composition of a polymerizable compound of the following formula    (I):

A-L-B  (I)

-   -   wherein    -   A is a group of the following formula (II)

-   -   -   X¹ is CO, CS, CH₂, or a group [X′Z]_(k), wherein X′ is an            oxygen atom, a sulfur atom or NH, Z is a straight chain or            branched C₁₋₄ alkylene group, and k is an integer of from 1            to 10;        -   R¹ is a hydrogen atom,            -   —COOM,            -   a straight chain or branched C₁₋₁₆ alkyl group which may                be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl                or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or                —SO₃M,            -   a C₃₋₆ cycloalkyl group which may be substituted by a                C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl                group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,            -   a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                substituted by —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,        -   R² is a hydrogen atom,            -   —COOM            -   a straight chain or branched C₁₋₁₆ alkyl group which may                be substituted by a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl                group, —COOM, —PO₃M, —O—PO₃M₂ and —SO₃M,            -   a C₃₋₆ cycloalkyl group which may be substituted by a                C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl                group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, or            -   a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                substituted by —COOM, —PO₃M, —O—PO₃M₂ and —SO₃M,

    -   L is a divalent C₂₋₁₂ alkenylene linker group, which may contain        1 to 3 carbonyl groups or heteroatoms selected from oxygen,        nitrogen and sulfur, and which may be substituted by a hydroxyl        group, a C₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,        wherein M is a hydrogen atom or a metal atom;

    -   B is selected from        -   (i) a group according to the definition of A,        -   (ii) a group of the following formula (III)

-   -   -   -   X² independently has the same meaning as defined for X¹                in formula (II),            -   R^(1′) and R^(2′) are independent from each other and                independently have the same meaning as defined for R¹                and R² in formula (II), R is a hydrogen atom,                -   a straight chain or branched C₁₋₁₆ alkyl group which                    may be substituted by a C₃₋₆ cycloalkyl group, a                    C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M,                    —O—PO₃M₂ or —SO₃M,                -   a C₃₋₆ cycloalkyl group which may be substituted by                    a C₁₋₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl                    group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,                -   a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                    substituted by —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,

        -   (iii) a group of the following formula (IV)

-   -   -   -   wherein            -   X³ is CO, —CH₂CO—, CS, or —CH₂CS—,            -   R^(1″) and R^(2″) which are independent from each other                and independently have the same meaning as defined for                R¹ and R² in formula (II), or

        -   (iv) a group [Z′X″ ]_(m)E,            -   wherein                -   Z′ is a straight chain or branched C₁₋₄ alkylene                    group,                -   X″ is an oxygen atom, a sulfur atom or NH,                -   E is a hydrogen atom,                -    PO₃M₂,                -    a straight chain or branched C₁₋₁₆ alkyl group                    which may be substituted by a C₃₋₆ cycloalkyl group,                    a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM,                    —PO₃M, —O—PO₃M₂ or —SO₃M,                -    a C₃₋₆ cycloalkyl group which may be substituted by                    a C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄                    heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,                -    a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                    substituted by —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, and                -   m is an integer of from 1 to 10; and

        -   wherein M of any one R¹, R², L, R and E, which M are            independent from each other, each represent a hydrogen atom            or a metal atom;

-   (b) 2 to 20 percent by weight based on the total weight of the    composition of a polymerizable compound of the following formula    (V):

A′-L′-A′   (V)

-   -   wherein the    -   A′ which are independent from each other, each represent a group        of the following formula (VI)

-   -   -   wherein        -   X²* independently has the same meaning as defined for X¹ in            formula (II),        -   R¹* and R²* are independent from each other and            independently have the same meaning as defined for R¹ and R²            in formula (II),        -   R* is a hydrogen atom,            -   a straight chain or branched C₁₋₁₆ alkyl group which may                be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl                or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or                —SO₃M,            -   a C₃₋₆ cycloalkyl group which may be substituted by a                C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl                group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,            -   a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                substituted by —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,

    -   L′ is a divalent C₂₋₁₂ alkylene linker group, which may contain        1 to 3 carbonyl groups or heteroatoms selected from oxygen,        nitrogen and sulfur, and which may be substituted by a hydroxyl        group, a C₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,        wherein M is a hydrogen atom or a metal atom;        -   wherein M of any one R¹*, R²*, L′ and R*, which M are            independent from each other, each represent a hydrogen atom            or a metal atom;

-   (c) 1 to 20 percent by weight based on the total weight of the    composition of one or more polymerizable monomers having one or more    acidic groups;

-   (d) 0.001 to 5 percent by weight based on the total weight of the    composition of an initiator system;

-   (e) 0.001 to 1 percent by weight based on the total weight of the    composition of a stabilizer; and

-   (f) 25 to 50 percent by weight based on the total weight of the    composition of a solvent mixture comprising water and an organic    solvent.

Furthermore, the present invention provides a use of a compositioncomprising

-   (a) a polymerizable compound of the following formula (I):

A-L-B  (I)

-   -   wherein    -   A is a group of the following formula (II)

-   -   -   X¹ is CO, CS, CH₂, or a group [X′Z]_(k), wherein X′ is an            oxygen atom, a sulfur atom or NH, Z is a straight chain or            branched C₁₋₄ alkylene group, and k is an integer of from 1            to 10;        -   R¹ is a hydrogen atom,            -   —COOM,            -   a straight chain or branched C₁₋₁₆ alkyl group which may                be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl                or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or                —SO₃M,            -   a C₃₋₆ cycloalkyl group which may be substituted by a                C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl                group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,            -   a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                substituted by —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,        -   R² is a hydrogen atom,            -   —COOM            -   a straight chain or branched C₁₋₁₆ alkyl group which may                be substituted by a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl                group, —COOM, —PO₃M, —O—PO₃M₂ and —SO₃M,            -   a C₃₋₆ cycloalkyl group which may be substituted by a                C₁₋₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl                group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, or            -   a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                substituted by —COOM, —PO₃M, —O—PO₃M₂ and —SO₃M,

    -   L is a divalent C₂₋₁₂ alkenylene linker group, which may contain        1 to 3 carbonyl groups or heteroatoms selected from oxygen,        nitrogen and sulfur, and which may be substituted by a hydroxyl        group, a C₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,        wherein M is a hydrogen atom or a metal atom;

    -   B is selected from        -   (i) a group according to the definition of A,        -   (ii) a group of the following formula (III)

-   -   -   -   X² independently has the same meaning as defined for X¹                in formula (II),            -   R^(1′) and R^(2′) are independent from each other and                independently have the same meaning as defined for R¹                and R² in formula (II),            -   R is a hydrogen atom,                -   a straight chain or branched C₁₋₁₆ alkyl group which                    may be substituted by a C₃₋₆ cycloalkyl group, a                    C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M,                    —O—PO₃M₂ or —SO₃M,                -   a C₃₋₆ cycloalkyl group which may be substituted by                    a C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄                    heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,                -   a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                    substituted by —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,

        -   (iii) a group of the following formula (IV)

-   -   -   -   wherein            -   X³ is CO, —CH₂CO—, CS, or —CH₂CS—,            -   R^(1″) and R^(2″) which are independent from each other                and independently have the same meaning as defined for                R¹ and R² in formula (II),

        -   (iv) a group [Z′X″ ]_(m)E,            -   wherein                -   Z′ is a straight chain or branched C₁₋₄ alkylene                    group,                -   X″ is an oxygen atom, a sulfur atom or NH,                -   E is a hydrogen atom,                -    PO₃M₂,                -    a straight chain or branched C₁₋₁₆ alkyl group                    which may be substituted by a C₃₋₆ cycloalkyl group,                    a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM,                    —PO₃M, —O—PO₃M₂ or —SO₃M,                -    a C₃₋₆ cycloalkyl group which may be substituted by                    a C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄                    heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,                -    a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                    substituted by —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, and                -   m is an integer of from 1 to 10; and

        -   wherein M of any one R¹, R², L, R and E, which M are            independent from each other, each represent a hydrogen atom            or a metal atom; and

-   (b) 2 to 20 percent by weight based on the total weight of the    composition of a polymerizable compound of the following formula    (V):

A′-L′-A′   (V)

-   -   wherein the    -   A′ which are independent from each other, each represent a group        of the following formula (VI)

-   -   -   wherein        -   X²* independently has the same meaning as defined for X¹ in            formula (II),        -   R¹* and R²* are independent from each other and            independently have the same meaning as defined for R¹ and R²            in formula (II),        -   R* is a hydrogen atom,            -   a straight chain or branched C₁₋₁₆ alkyl group which may                be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl                or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or                —SO₃M,            -   a C₃₋₆ cycloalkyl group which may be substituted by a                C₁₁ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group,                —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,            -   a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be                substituted by —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,

    -   L′ is a divalent C₂₋₁₂ alkylene linker group, which may contain        1 to 3 carbonyl groups or heteroatoms selected from oxygen,        nitrogen and sulfur, and which may be substituted by a hydroxyl        group, a C₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,        wherein M is a hydrogen atom or a metal atom;        -   wherein M of any one R¹*, R²*, L′ and R*, which M are            independent from each other, each represent a hydrogen atom            or a metal atom;

-    for the preparation of an aqueous dental composition.

The present invention is based on the recognition that a combination ofa compound of formula (I) and a compound of formula (V) as defined aboveprovides surprisingly improved wetting properties, among others due toimproved penetration properties. It has been found that wetting of adental surface by the aqueous dental composition and viscosity of theaqueous dental composition can be synergistically improved by acombination of polymerizable compounds of formulae (I) and (V) in anaqueous solvent mixture. Accordingly, the application of the aqueousdental composition on a dental surface is simplified and the wetting ofthe dental surface is improved.

Moreover, the specific combination of polymerizable compounds offormulae (I) and (V) is the basis for high storage stability of theaqueous dental composition and stability after curing in the mouth of apatient.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The term “aqueous dental composition” relates to a compositioncomprising a solvent mixture comprising an organic solvent and water.Preferably, the solvent mixture comprises water in an amount of at least1 percent by weight based on the total weight of the composition.Commercially available organic solvents may contain a substantial amountof water and therefore may serve as a source for the water contained inthe solvent mixture. However, additional water, that is water which doesnot derive from the organic solvent of the solvent mixture, ispreferably added to the organic solvent.

The “pH of at most 7” of the aqueous dental composition according to theinvention may be adjusted by any means known in the art, e.g. by addingpredetermined amounts of one or more acidic or alkaline compounds to theaqueous dental composition. In this context, the term “acidic compounds”denotes compounds having a pK_(a) value within the range of about −10 to50. The term “alkaline compounds” denotes compounds having a pK_(b)value within the range of about −34 to 14. Examples of suitableinorganic acids are sulfuric acid, phosphonic acid, phosphoric acid,hydrochloric acid, nitric acid and the like, which may be used alone orin combination with each other. Examples of suitable organic acidiccompounds are carboxylic acids which are preferably selected from thegroup consisting of formic acid, acetic acid, lactic acid, citric acid,itaconic acid, poly(meth)acrylic acid, itaconic acid, maleic acid,polyvinyl phosphonic acid, polyvinyl phosphoric acid,trifluoromethanesulfonic acid, toluenesulfonic acid, methanesulfonicacid, succinic acid, malic acid, tannic acid, toluene sulfonic acid,adipic acid, tartaric acid and ascorbic acid.

Examples of suitable inorganic alkaline compounds are alkali metal orearth alkaline metal hydroxides, for example sodium hydroxid, potassiumhydroxide, calcium hydroxide or barium hydroxide, which may be usedalone or in combination with each other. Examples of suitable organicalkalines are e.g. organic primary and tertiary amines such astriethanolamine and tris(hydroxymethyl)-aminomethan (TRIS). The setpH-value of the aqueous dental composition may be stabilized by means ofa typical chemical buffer system, that is a combination of a weakorganic or inorganic acid having a pK_(a) value at a temperature of 20°C. within the range of about 9 to 50 and its corresponding salt.

Alternatively, the buffer system may be in the form of a Norman Goodsbuffer (Good's buffer) representing organic compounds having a pK_(a)value at a temperature of 20° C. in a range between about 6 and 8,having biochemical inertness and being suitable for application in abiological system such as the human body. Examples for typical chemicalbuffer systems are acidic acid/acetate buffer,dihydrogenphosphate/monohydrogenphosphate buffer or a citricacid/citrate buffer.

Examples for Good's buffers are4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES),2-(N-morpholino)ethanesulfonic acid (MES) orN-cyclohexyl-3-aminopropanesulfonic acid (CAPS). In connection with theterm “pH-value” it is noted that the pH-value/system typically relatesto aqueous systems wherein water is the main compound, i.e. present inan amount of about 90 percent by weight. In the present aqueous dentalcomposition, water is typically not the main component. However, allpH-values indicated in the present application relate to pH-valuesdetermined by suitable standard means for determining the pH-value ofaqueous systems, e.g. by means of a glass electrode.

Besides of the aforementioned organic acidic and alkaline compounds, thecompounds according to any one of items (a), (b), (c), (d), (e) and (f)may be applied for setting the pH of the present aqueous dentalcomposition. For example, the polymerizable compound of formulae (I) and(V) according to (a) and (b) may have an acidic functional group such as—COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, wherein M may represent a hydrogen atomand thus influences the pH of the present aqueous dental composition.Besides, the polymerizable monomer according to (c) mandatory has one ormore acidic groups. On the other hand, the polymerizable compounds offormulae (I) and (V) according to (a) and (b) mandatory comprise analkaline functional group in the form of a tertiary amine group.

The term “polymerizable” as used herein in connection with“polymerizable compounds” of formulae (I) and (V), “polymerizablemonomer having one or more acidic group”, “polymerizable group” and“polymerizable double bond” respectively mean any compound, monomer,functional group or double bond capable of radical polymerization.Preferably, capability of radical polymerization is provided by acarbon-carbon double bond. Examples of the polymerizable carbon-carbondouble bonds include vinyl, conjugated vinyl, allyl, acryl, methacryland styryl. More preferably, the polymerizable carbon-carbon doublebound is selected from the group consisting of acryl, methacryl, allyland styryl.

The term “alkenylene” as used herein in connection with group L ofcompound of formula (I) means a divalent group derived from a straight-or branched-chain C₂₋₁₂ hydrocarbon which contains at least onecarbon-carbon double bond.

The term “alkylene” as used herein in connection with group L′ ofcompound of formula (V) means a divalent group derived from a straight-or branched-chain saturated C₂₋₁₂ hydrocarbon.

In both of the above defined “alkenylene” and “alkylene” defined for Land L′, apart from the 2 to 12 carbon atoms of the hydrocarbon, inaddition, the hydrocarbon may contain further carbon atoms deriving fromoptional carbonyl groups incorporated therein, optional substitutionwith C₆₋₁₄ aryl group and/or an optional —COOM group.

The compounds of formulae (I) and (V) are hydrolysis-stable. This meansthat these compounds are stable to hydrolysis in an acidic medium, suchas in a dental composition. Specifically, these compounds do not containgroups such as ester groups which hydrolyze in aqueous media at pH 3 atroom temperature within one month.

The pH of the present aqueous dental composition is suitably set in viewof the application, e.g. etching, but also in view of chemicalcompatibility with the further components comprised in the compositionand/or in the restorative material. Preferably, the aqueous dentalcomposition according to the present invention has a pH of less than6.5, more preferably pH is from 1 to 6, even more preferably from 2 to5.

The present invention provides an aqueous dental composition having a pHof at most 7. The aqueous dental composition of the present invention ispolymerizable or copolymerizable by a radical polymerization. Theaqueous dental composition may be a dental material to be used in theoral cavity. Preferably, the present aqueous dental composition isselected from a dental adhesive composition, a dental bonding agent, adental primer, a dental infiltrant, a pit and fissure sealant, a dentaldesensitizing composition, a pulp capping composition, a dentalcomposite, dental glass ionomer cement, a dental cement, a seal andprotecting composition for naked tooth necks, and a dental root canalsealer composition.

According to (a), the present aqueous dental composition having a pH ofat most 7 comprises a polymerizable compound of the following formula(I). The aqueous dental composition may comprise one or more compoundsof formula (I). The aqueous dental composition of the present inventioncomprises the polymerizable compound(s) of formula (I) in an amount offrom 1 to 70 percent by weight based on the total weight of thecomposition. Preferably, the aqueous dental composition comprises one ormore compounds of formula (I) in an amount of from 10 to 60 percent byweight, most preferably 20 to 60 percent by weight based on the totalweight of the composition.

The amount of compound of formula (I) may be suitably selected in viewof the intended application purpose. For example, a dental adhesivecomposition may comprise 1 to 70 percent by weight, preferably 5 to 20percent by weight, based on the total weight of the entire compositionof one or more compounds of formula (I). A dental bonding agent maycomprise 1 to 70 percent by weight, preferably 5 to 20 percent byweight, based on the total weight of the entire composition of one ormore compounds of formula (I). A dental primer may comprise 1 to 70percent by weight, preferably 5 to 20 percent by weight, based on thetotal weight of the entire composition of one or more compounds offormula (I). A dental infiltrant may comprise 1 to 70 percent by weight,preferably 5 to 20 percent by weight, based on the total weight of theentire composition of one or more compounds of formula (I). A pit andfissure sealant may comprise 1 to 70 percent by weight, preferably 5 to20 percent by weight, based on the total weight of the entirecomposition of one or more compounds of formula (I). A dentaldesensitizing composition may comprise 1 to 70 percent by weight,preferably 5 to 20 percent by weight, based on the total weight of theentire composition of one or more compounds of formula (I). A pulpcapping composition may comprise 1 to 50 percent by weight, preferably 5to 20 percent by weight, based on the total weight of the entirecomposition of one or more compounds of formula (I). A dental compositemay comprise 1 to 30 percent by weight, preferably 3 to 10 percent byweight, based on the total weight of the entire composition of one ormore compounds of formula (I). A dental glass ionomer cement maycomprise 1 to 30 percent by weight, preferably 2 to 10 percent byweight, based on the total weight of the entire composition of one ormore compounds of formula (I). A dental cement may comprise 1 to 30percent by weight, preferably 3 to 10 percent by weight, based on thetotal weight of the entire composition of one or more compounds offormula (I). A seal and protecting composition for naked tooth necks maycomprise 1 to 70 percent by weight, preferably 5 to 20 percent byweight, based on the total weight of the entire composition of one ormore compounds of formula (I). A dental root canal sealer compositionmay comprise 1 to 70 percent by weight, preferably 5 to 20 percent byweight, based on the total weight of the entire composition of one ormore compounds of formula (I).

An aqueous dental composition comprises a compound according to thefollowing formula (I):

A-L-B  (I).

In formula (I), A is a specific polymerizable group which is linked by adivalent linker group L to a group B. The group B may be polymerizable.

According to the present invention, A is a group of the followingformula (II)

Accordingly, any compound of formula (I) is characterized by an allylgroup bonded to a nitrogen atom and a further specific group having apolymerizable double bond which is bonded via X¹ to the same nitrogenatom. The specific arrangement of the polymerizable double bond of theallyl group and a further polymerizable double bond which is bonded tothe same nitrogen atom activates the allyl bond so that the allyl bondtakes part in the radical polymerization reaction during curing.

In formula (II), the jagged bond indicates that R¹ may be in cis ortrans configuration relative to X¹. In formulae (III), (IV) and (VI),the jagged bond has an analogous meaning. In particular, in formula(III), the jagged bond indicates that R^(1′) may be in cis or transconfiguration relative to X¹. In formula (IV), the jagged bond indicatesthat R^(1″) may be in cis or trans configuration relative to X³. Informula (VI), the jagged bond indicates that R¹* may be in cis or transconfiguration relative to X²*.

In formula (II), X¹ is CO, CS, CH₂, or a group [X′Z]_(k), wherein X′ isan oxygen atom, a sulfur atom or NH, Z is a straight chain or branchedC₁₋₄ alkylene group, and k is an integer of from 1 to 10. Preferably, informula (II), X¹ is CO.

In case X¹ is CO, CS, CH₂ in formula (II), a polymerizable double bondis present which may take part with the allyl group directly bonded tothe nitrogen atom of the group of formula (II) in a cyclopolymerizationreaction according to the following Scheme 1.

In case X¹ is a group [X′Z]_(k) in formula (II), it is preferred that LBprovides a polymerizable double bond which may take part with the allylgroup directly bonded to the nitrogen atom of the group of formula (II)in a cyclopolymerization reaction. Preferably, X′ is an oxygen atom.Preferred examples for a straight chain or branched C₁₋₄ alkylene groupfor Z are an ethylene group and a propylene group. Preferably, k is aninteger of from 1 to 4.

According to a preferred embodiment, in formula (II), X¹ is CO.

In formula (II), R¹ is a hydrogen atom, —COOM, a straight chain orbranched C₁₋₁₆ alkyl group which may be substituted by a C₃₋₆ cycloalkylgroup, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or—SO₃M, a C₃₋₆ cycloalkyl group which may be substituted by a C₁₋₁₆ alkylgroup, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or—SO₃M, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be substitutedby —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M.

For R¹ of formula (II), the straight chain or branched C₁₋₁₆ alkyl groupmay e.g. be methyl, ethyl, n-propyl, i-propyl, n-butyl, isobutyl,tert-butyl, sec-butyl, pentyl or hexyl. An aryl group may, for example,be a phenyl group or a naphthyl group. A C₃₋₁₄ heteroaryl group maycontain 1 to 3 heteroatoms selected from nitrogen, oxygen and sulfur.

Preferably, R¹ is a hydrogen atom, a straight chain or branched C₁₋₈alkyl group which may be substituted by a C₄₋₆ cycloalkyl group, a C₆₋₁₀aryl or C₄₋₁₀ heteroaryl group, a C₄₋₆ cycloalkyl group which may besubstituted by a C₁₋₆ alkyl group, a C₆₋₁₀ aryl or C₄₋₁₀ heteroarylgroup or a C₆₋₁₀ aryl group. More preferably, R¹ is a hydrogen atom, astraight chain or branched C₁₋₄ alkyl group which may be substituted bya cyclohexyl group or a phenyl group, or a cyclohexyl group which may besubstituted by a C₁₋₄ alkyl group. Most preferably, R¹ is a hydrogenatom.

In formula (II), R² is a hydrogen atom, —COOM, a straight chain orbranched C₁₋₁₆ alkyl group which may be substituted by a C₆₋₁₄ aryl orC₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ and —SO₃M, a C₃₋₆cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,or a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be substituted by—COOM, —PO₃M, —O—PO₃M₂ and —SO₃M.

For R² of formula (II), the C₁₋₁₆ alkyl group may e.g. be methyl, ethyl,n-propyl, i-propyl, n-butyl, isobutyl, tert-butyl sec-butyl, pentyl orhexyl. An aryl group may, for example, be a phenyl group or a naphthylgroup. A C₃₋₁₄ heteroaryl group may contain 1 to 3 heteroatoms selectedfrom nitrogen, oxygen and sulfur.

Preferably, R² is a hydrogen atom, a straight chain or branched C₁₋₈alkyl group which may be substituted by a C₄₋₆ cycloalkyl group, a C₆₋₁₀aryl, C₄₋₁₀ heteroaryl group or —COOM, a C₄₋₆ cycloalkyl group which maybe substituted by a C₁₋₆ alkyl group, a C₆₋₁₀ aryl, C₄₋₁₀ heteroarylgroup or —COOM, or a C₆₋₁₀ aryl group which may be substituted by —COOM.More preferably, R² is a hydrogen atom, a straight chain or branched C₁alkyl group which may be substituted by a cyclohexyl group, a phenylgroup or —COOM, or a cyclohexyl group which may be substituted by a C₁₋₄alkyl group. Even more preferably, R² a hydrogen atom, a straight chainor branched C₁₋₄ alkyl group which may be substituted by —COOM, morepreferably a hydrogen atom, a methyl group or —CH₂—COOM. Mostpreferably, R² is a hydrogen atom.

The following groups are preferred groups of formula (II), wherein M isa hydrogen atom or a metal atom:

The group of formula (IIb) is particularly preferred.

In formula (I), L is a divalent C₂₋₁₂ alkenylene linker group, which maycontain 1 to 3 carbonyl groups or heteroatoms selected from oxygen,nitrogen and sulfur, and which may be substituted by a hydroxyl group, aC₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, wherein M is ahydrogen atom or a metal atom.

For L of formula (I), specific examples of a divalent C₂₋₁₂ alkenylenelinker group are straight chain or branched C₂₋₁₂ alkenylene groups suchas ethenylene, propenylene, butenylene, pentenylene or hexenylene, orcyclic C₃₋₁₂ alkenylene groups such as cyclopropenylene,cyclobutenylene, cyclopentenylene, cyclohexenylene. Preferably, divalentlinker group L is a straight chain or branched C₂₋₁₂alkenylene group.

It is preferred that divalent linker group L is a straight chain C₂₋₈alkenylene linker group, which may optionally include one or more —CO—group. More preferably, a divalent linker group L is —CH₂—CH═CH—CH₂— or—CO—CH═CH—CO—. The substituents of the C═C double bond are preferably intrans configuration. Most preferably, L is —CH₂—CH═CH—CH₂— in transconfiguration.

In formula (I), B is selected from (i) a group according to thedefinition of A, (ii) a group of the following formula (III), (iii) agroup of the following formula (IV) and (iv) a group of the formula[Z′X″]_(m)E.

When B is a group according to formula (II) in the definition of A, thenB may be the same or different from the group A present in apolymerizable compound of formula (I). Specifically, B may be a group ofthe above formula (II) wherein an allyl group is bonded to a nitrogenatom, and a further group having a polymerizable double bond is bondedto the same nitrogen atom.

When B is a group according to formula (II) in the definition of A, X¹is CO, CS, CH₂, or a group [X′Z]_(k), wherein X′ is an oxygen atom, asulfur atom or NH, Z is a straight chain or branched C₁ alkylene group,and k is an integer of from 1 to 10.

According to a preferred embodiment of B being a group according toformula (II) in the definition of A, X¹ is CO.

When B is a group according to formula (II) in the definition of A, R¹independently has the same meaning as defined above for formula (II).

When B is a group according to formula (II) in the definition of A, R²independently has the same meaning as defined above for formula (II).

When B is a group of the formula (III), B is as follows:

In formula (III), X² has the same meaning as defined for X¹ in formula(II). Specifically, when B is a group according to formula (III), X² isCO, CS, CH₂, or a group [X′Z]_(k), wherein X′ is an oxygen atom, asulfur atom or NH, Z is a straight chain or branched C₁₋₄ alkylenegroup, and k is an integer of from 1 to 10. X′, Z and k of a group offormula (III) maybe the same or different of X′, Z and k of group offormula (II) present as A in the polymerizable compound of formula (I).

Preferably, in formula (III), X′ is an oxygen atom. Preferred examplesfor a straight chain or branched C₁₋₄ alkylene group for Z are anethylene group and a propylene group. Preferably, k is an integer offrom 1 to 4.

In formula (III), R¹ and R² are independent from each other andindependently have the same meaning as defined for R¹ and R² in formula(II).

Specifically, when B is a group according to formula (III), R¹ is ahydrogen atom, —COOM, a straight chain or branched C₁₋₆ alkyl groupwhich may be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl orC₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₃₋₆cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be substituted by —COOM,—PO₃M, —O—PO₃M₂ or —SO₃M.

According to a preferred embodiment when B is a group according toformula (III), R^(1′) is a hydrogen atom. In case R^(1′) is a C₁₋₆ alkylgroup, the C₁₋₆ alkyl group is preferably substituted by —COOM.

When B is a group according to formula (III), R^(2′) is a hydrogen atom,—COOM, a straight chain or branched C₁₋₆ alkyl group which may besubstituted by a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M,—O—PO₃M₂ and —SO₃M, a C₃₋₆ cycloalkyl group which may be substituted bya C₁₋₆ alkyl group, a C₁₋₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M,—O—PO₃M₂ or —SO₃M, or a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which maybe substituted by —COOM, —PO₃M, —O—PO₃M₂ and —SO₃M,

According to a preferred embodiment of B being a group according toformula (III), R^(2′) is a hydrogen atom or a straight chain or branchedC₁₋₆ alkyl group, more preferably a hydrogen atom or a straight chain orbranched C₁₋₄ alkyl group, most preferably a hydrogen group or a methylgroup.

In formula (III), R is a hydrogen atom, a straight chain or branchedC₁₋₁₆ alkyl group which may be substituted by a C₃₋₆ cycloalkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, aC₃₋₆ cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, aC₆₋₁₄ aryl group which may be substituted by —COOM, —PO₃M, —O—PO₃M₂ or—SO₃M.

Preferably, R is a hydrogen atom, a straight chain or branched C₁₋₈alkyl group which may be substituted by a C₄₋₆ cycloalkyl group, a C₆₋₁₀aryl or C₄₋₁₀ heteroaryl group, a C₄₋₆ cycloalkyl group which may besubstituted by a C₁₋₆ alkyl group, a C₆₋₁₀ aryl or C₄₋₁₀ heteroarylgroup or a C₆₋₁₀ aryl group. More preferably, R is a hydrogen atom, astraight chain or branched C₁₋₄ alkyl group which may be substituted bya cyclohexyl group or a phenyl group, or a cyclohexyl group which may besubstituted by a C₁₋₄ alkyl group. Most preferably, R is a hydrogenatom, methyl, ethyl, cyclohexyl or benzyl.

Preferred groups of B of the formula (III) are as follows wherein M is ahydrogen atom or a metal atom:

When B is a group of the formula (IV), B is as follows:

In formula (IV), X³ is CO, —CH₂CO—, CS or —CH₂CS—, According to apreferred embodiment, X³ is CO or —CH₂CO—.

In formula (IV), R^(1″) and R^(2″) are independent from each other andindependently have the same meaning as defined for R¹ and R² in formula(II).

Specifically, when B is a group according to formula (IV), R^(1″) is ahydrogen atom, —COOM, a straight chain or branched C₁₋₁₆ alkyl groupwhich may be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl orC₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₃₋₆cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be substituted by —COOM,—PO₃M, —O—PO₃M₂ or —SO₃M.

According to a preferred embodiment when B is a group according toformula (IV), R^(1″) is a hydrogen atom. In case R^(1″) is a C₁₋₁₆ alkylgroup, the C₁₋₁₆ alkyl group is preferably substituted by —COOM.

When B is a group according to formula (IV), R^(2″) is a hydrogen atom,—COOM, a straight chain or branched C₁₋₁₆ alkyl group which may besubstituted by a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M,—O—PO₃M₂ and —SO₃M, a C₃₋₆ cycloalkyl group which may be substituted bya C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM,—PO₃M, —O—PO₃M₂ or —SO₃M, or a C₆₋₁₄ aryl group which may be substitutedby —COOM, —PO₃M, —O—PO₃M₂ and —SO₃M,

According to a preferred embodiment of B being a group according toformula (IV), R^(2″) is a hydrogen atom or a methyl group.

Preferred groups of formula (IV) are selected from the group consistingof:

wherein M is a hydrogen atom or a metal atom.

According to the definition of the present invention, the M which areindependent from each other, each represent a hydrogen atom or a metalatom. The metal atom is preferably an alkali metal or an alkaline earthmetal. Specific examples of the alkali metal are lithium, sodium, andpotassium. Specific examples of the alkaline earth metal are calcium,strontium and magnesium. The metal atom may also be tin.

When B is a group [Z′X″]_(m)E, the meaning of Z′, X″, m, and E is asfollows. Z′ is a straight chain or branched C₁₋₄ alkylene group.Specific examples of the C₁₋₄ alkylene groups are methylene, ethylene,propylene and butylene. X″ is an oxygen atom, a sulfur atom or NH.

E is a hydrogen atom, PO₃M₂, a straight chain or branched C₁₋₁₆ alkylgroup which may be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ arylor C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₃₋₆cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be substituted by —COOM,—PO₃M, —O—PO₃M₂ or —SO₃M.

In formula group [Z′X″]_(m)E, m is an integer of from 1 to 10.

According to a preferred embodiment, B is (i) a group according to thedefinition of A. According to a particularly preferred embodiment,compound of formula (I) is N,N′-diallyl-1,4-bisacrylamido-(2E)-but-2-en(BAABE) having the following structural formula:

The polymerizable compound of formula (I) may be prepared according tothe following Scheme 2, wherein A** and B** represent polymerizablegroups, and C and G represent groups which are suitable for providing alinkage between A** and L and L and B** respectively, as shown in thefollowing Scheme 2:

A**-C+G-L-G+C—B**→A**-L-B**   Scheme 2

The linkage may be formed by a substitution reaction, an additionreaction or a condensation reaction. The reaction may involve theformation of an amine bond, an amide bond or an urethane bond.Preferably, the reaction is a substitution reaction and involves theformation of an amine bond.

The polymerizable compound of formula (I) may be prepared by a reactionwherein a stoichiometric mixture of compound A**-C and G-L-G is reactedand then the reaction product is reacted with a compound C—B**.Alternatively, it is possible to prepare a polymerizable compound offormula (I) by a reaction wherein a mixture of compound B**—C and G-L-Gis reacted first, and then the reaction product is reacted with compoundA**-C. Or, according to a particularly preferred alternative, A**-C andC—B** are identical compounds, wherein about two molar equivalents ofthese compounds are reacted with one molar equivalent of G-L-G.Depending on the nature of A** and B**, further reaction steps may berequired in order to arrive at the above defined groups A and B, or A**and B** are identical with A and B.

An exemplary pathway for the preparation ofN,N′-diallyl-1,4-bisacrylamido-(2E)-but-2-en (BAABE) is depicted in thefollowing Scheme 3:

The reaction may be performed in accordance with, for example, themethods described in Jerry March “Advanced Organic Chemistry” 6^(th)Edition, John Wiley & Sons, INC., 2007 and Richard C. Larock“Comprehensive Organic Transformation”, VCH Publishers, INC., 2010,2^(nd) revised edition, or a method conforming to the methods describedabove. The reaction may be carried out in a solvent which is capable ofdissolving the reactants. For the first step of reacting1,4-dibromo-2-butene with allylamine, a suitable solvent is e.g.acetonitrile. For the second step of reacting the product of step 1 withacryloyl chloride, a suitable solvent is e.g. dichloromethane. For thesecond step, a suitable halogen trialkylsilane is chlorotrimethylsilane,wherein a suitable organic base such as triethylamine is added andoptionally an antioxidant such as 2,6-di-tert-butyl-methylphenol isadded for stabilization. After acrylation with acryloyl chloride, asuitable acid such as hydrochloric acid is added.

According to (b), the present aqueous dental composition having a pH ofat most 7 comprises a polymerizable compound of the following formula(V). The aqueous dental composition may comprise one or more compoundsof formula (V). The aqueous dental composition of the present inventioncomprises the polymerizable compound(s) of formula (V) in an amount offrom 2 to 20 percent by weight based on the total weight of thecomposition. Preferably, the aqueous dental composition comprises one ormore compounds of formula (V) in an amount of from 3 to 15 percent byweight, most preferably 4 to 10 percent by weight based on the totalweight of the composition.

A compound of formula (V) is according to the following formula (V):

A′-L′-A′  (V).

In formula (V), A′ is a specific polymerizable group which is linked bydivalent linker group L′ to a group A′ which is the same or differentpolymerizable group as the first mentioned polymerizable group A′.

According to the present invention, A′ is a group of the followingformula (VI)

Accordingly, any compound of formula (V) is characterized by a group offormula (VI) having a polymerizable double bond which is bonded to thenitrogen atom via X².

In formula (VI), R¹* and R²* are independent from each other andindependently have the same meaning as defined for R¹ and R² in aboveformula (II). Furthermore, X²* and R* independently have the samemeaning as defined for X² and R in above formula (III).

In formula (VI), L′ is a divalent C₂₋₁₂ alkylene linker group, which maycontain 1 to 3 carbonyl groups or heteroatoms selected from oxygen,nitrogen and sulfur, and which may be substituted by a hydroxyl group, aC₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, wherein M is ahydrogen atom or a metal atom.

For L′ of formula (VI), specific examples of a divalent C₂₋₁₂ alkylenelinker group are straight chain or branched C₂₋₁₂ alkylene groups suchas ethylene, propylene, butylene, pentylene or hexylene, or cyclic C₃₋₁₂alkylene groups such as cyclopropylene, cyclobutylene, cyclopentylene,cyclohexylene. Preferably, divalent linker group L′ is a straight chainor branched C₂₋₁₂ alkylene group.

It is preferred that divalent linker group L′ is —(CH₂)₂₋₈— or—CO—(CH₂)₂₋₈—CO—. More preferably, divalent linker group L′ is —(CH₂)₃—or —CO—CH—CO—, most preferably n-propylene.

In contrast to formula (II), for formula (VI), the particular preferredselection for R²* differs from that for R² of formula (II) in that it isparticularly preferred that R²* is a hydrogen atom.

For example, compounds of formula (V) may be bisacrylamide compoundshaving the following structural formulae:

or bismethacrylamide compounds having the following structural formulae:

According to a preferred embodiment, in formula (VI), for X²*, R¹*, R²*and R²*, at least one of the following features is selected:

-   -   X²* is CO,    -   R* is an ethyl group,    -   R¹* is a hydrogen atom,    -   R²* is a hydrogen atom.

According to a particularly preferred embodiment, compound of formula(V) is N,N′-diethyl-1,3-bisacrylamido-propan (BADEP).

The polymerizable compound of formula (V) may be prepared in ananalogous way as explained for compound of formula (I) above.

The specific combination of compounds of formulae (I) and (V) providesfor a synergistically improvement of both wetting of a dental surface bythe aqueous dental composition and viscosity of the aqueous dentalcomposition. This in turn results in a simplified and facilitatedapplication of the aqueous dental composition on a dental surface. Inaddition, the penetration of the dental surface is improved.

Furthermore, owing to the specific combination of compounds of formulae(I) and (V), both the uncured and the cured dental composition providesfor an improved stability. This is because compounds of formulae (I) and(V) do not comprise groups being susceptible to cleavage under acidicconditions.

According to (c), the aqueous dental composition comprises apolymerizable monomer having one or more acidic groups. The aqueousdental composition may comprise one or more polymerizable monomer(s)having one or more acidic groups. The aqueous dental composition of thepresent invention comprises the polymerizable monomer(s) having one ormore acidic groups in an amount of from 1 to 20 percent by weight basedon the total weight of the composition. Preferably, the aqueous dentalcomposition comprises one or more polymerizable monomer(s) having one ormore acidic groups in an amount of from 4 to 19 percent by weight, mostpreferably 8 to 18 percent by weight based on the total weight of thecomposition.

The polymerizable monomer having one or more acidic groups preferablyhas a group imparting acidity to said monomer. More preferably, theacidic group is selected from the group consisting of a phosphoric acidester group, a phosphonic acid group, a sulfonic acid group and acarboxylic acid group.

Furthermore, the polymerizable monomer having one or more acidic groupshas at least one polymerizable double bond. The polymerizable monomerhaving one or more acidic groups may be selected from the group of thefollowing compounds (IX), (X) and (XI).

Phosphoric acid ester group containing polymerizable compounds having atleast one polymerizable double bond preferably have the followingformula (IX):

wherein

the moieties Y independent from each other represent a hydrogen atom ora moiety of the following formulae (Y*), (Y**) or (Y***):

wherein

Z₁ is COOR⁵, COSR⁶, CON(R⁵)₂, CONR⁵R⁶, or CONHR⁵, wherein R⁵ and R⁶independently represent a hydrogen atom, a C₁₋₁₈ alkyl group optionallysubstituted by a C₃₋₈ cycloalkyl group, an optionally substituted C₃₋₈cycloalkyl group, an optionally substituted C₄₋₁₈ aryl or heteroarylgroup, an optionally substituted C₅₋₁₈ alkylaryl or alkylheteroarylgroup, or an optionally substituted C₇₋₃₀ aralkyl group, whereby two R⁵residues may form together with the adjacent nitrogen atom to which theyare bound a 5- to 7-membered heterocyclic ring which may contain furthernitrogen atoms or an oxygen atoms, and whereby the optionallysubstituted groups may be substituted by 1 to 5 Cis alkyl group(s);

R⁷ and R⁸ independently represent a hydrogen atom, an optionallysubstituted C₁₋₈ alkyl group, an optionally substituted C₃₋₁₈ cycloalkylgroup, an optionally substituted C₅₋₁₈ aryl or heteroaryl group, anoptionally substituted C₅₋₁₈ alkylaryl or alkylheteroaryl group, anoptionally substituted C₇₋₃₀ aralkyl group, whereby the optionallysubstituted groups may be substituted by 1 to 5 C₁₋₅ alkyl group(s);

L* represents an (a+b)-valent organic residue (whereby b is 1 when Y informula (IX) is within the round brackets) containing 2 to 45 carbonatoms and optionally heteroatoms such as oxygen, nitrogen and sulfuratoms, the carbon atoms including a+b carbon atoms selected from primaryand secondary aliphatic carbon atoms, secondary alicyclic carbon atoms,and aromatic carbon atoms, each of the a+b carbon atoms linking aphosphate or a moiety of any one of formula (Y*), (Y**) and (Y***); a isan integer of from 1 to 10, preferably 1 to 5; b is an integer of from 1to 10, preferably 1 to 5; provided that at least one Y is not hydrogen.The preparation of such compounds wherein Y═Y* is known from EP-A 1 548021.

Furthermore, the polymerizable monomer having one or more acidic groupsmay be selected from:

-   1) phosphonic acid group containing polymerisable acidic compounds    of the following formula (X):

wherein

the moiety Y₁ represents a moiety of the following formulae (Y₁*),(Y₁**) or (Y₁***):

Z₂ independently has the same meaning as defined for Z₁;

R⁹ and R¹⁰ independently have the same meaning as defined for R⁷ and R⁸;

L₁ represents a (c+d) valent organic residue containing 2 to 45 carbonatoms and optionally heteroatoms such as oxygen, nitrogen and sulfur,the carbon atoms including c+d carbon atoms selected from primary andsecondary aliphatic carbon atoms, secondary alicyclic carbon atoms, andaromatic carbon atoms, each of the c+d carbon atoms linking aphosphonate or a moiety of any one of formula (Y₁*), (Y₁**) and (Y₁***);and c and d independently represent integers of from 1 to 10; and/or

-   2) sulfonic acid group containing polymerisable acidic compounds of    the following formula (XI):

wherein

the moiety Y₂ represents a moiety of the following formulae (Y₂*),(Y₂**) or (Y₂***):

Z₃ independently has the same meaning as defined for Z₁.

R¹¹ and R¹² independently have the same meaning as defined for R⁷ andR⁸;

L₂ represents an (e+f) valent organic residue containing 2 to 45 carbonatoms and optionally heteroatoms such as oxygen, nitrogen and sulfuratoms, the carbon atoms including e+f carbon atoms selected from primaryand secondary aliphatic carbon atoms, secondary alicyclic carbon atoms,and aromatic carbon atoms, each of the e+f carbon atoms linking asulphonate or a moiety of any one of formula (Y₂*), (Y₂**) and (Y₂***);and

e and f independently represent an integer of from 1 to 10.

It is preferred to select compounds of formula (IX), (X) and (XI) withthe proviso that they do not contain ester groups, or at least onlyester groups which do not hydrolyze in aqueous media at pH 3 at roomtemperature within one month, such as the phosphoric acid ester group ofcompounds of formula (IX). Thereby, an advantageous stability of theaqueous dental composition having a pH of at most 7 in terms ofshelf-life stability of the uncured dental composition as well asstability after curing in the mouth of a patient is ensured. Therefore,particularly preferred are compounds of formula (IX) excluding themoiety of formula Y*** and the moiety of formula Y* wherein Z₁ is COOR⁵or COSR⁶, compounds of formula (X) excluding the moiety of formula Y₁***and the moiety of formula Y₁* wherein Z₂ is COOR⁵ or COSR⁶ as well ascompounds of formula (XI) excluding the moiety of formula Y₂*** and themoiety of formula Y₂* wherein Z₃ is COOR⁵ or COSR⁶.

Carboxylic acid group containing polymerizable compounds having at leastone polymerizable double bond may be selected e.g. from acrylic acid andmethacrylic acid.

From the phosphoric acid ester group containing polymerizable compoundhaving at least one polymerizable double bond, compounds of formula(IX′) characterized by one of the following formulae are particularlypreferred:

wherein Z₁ is defined as above, and L* is an optionally substitutedalkylene group. More preferably, Z₁ is methyl, and L* is a C₄ to C₁₆alkylene group. Even more preferably, L* is a C₈ to C₁₂ alkylene group.

From the sulfonic acid group containing polymerizable compound having atleast one polymerizable double bond, compounds of formula (XI′)characterized by one of the following formulae are particularlypreferred:

In a preferred embodiment, according to (c), the polymerizable monomerhaving one or more acidic groups is a polymerizable phosphoric acidester according to formula (IX).

According to (d), the aqueous dental composition comprises aphotoinitiator system.

The term “polymerization initiator system” refers to a system comprisingat least a 1,2-diketone photoinitiator compound.

Preferably, the polymerization initiator system comprises:

-   (d-i) an 1,2-diketone photoinitiator compound having a light    absorption maximum in the range from 300 to 500 nm;-   (d-ii) optionally a coinitiator compound; and-   (d-iii) optionally a polymerization initiator auxiliary substance.

The photoinitiator system may comprise one or more of any one ofcomponents (d-i), (d-ii) and (d-iii).

The term “1,2-diketone photoinitiator” denotes any chemical compoundhaving 1,2-diketone functional group, which compound forms free radicalswhen activated, e. g. by exposure to light or interaction with acoinitiator and optionally a polymerization initiator auxiliarysubstance in a photochemical process.

1,2-diketone photoinitiator according to (d-i) belongs to the Norrishtype I photoinitiators which provide free radical intermediates byphotochemical abstraction. Preferably, the 1,2-diketone photoinitiatorcompound according to (d-i) is selected from the group consisting ofcamphorquinone, benzil, 2,2′-3 3′- and 4,4′-dihydroxylbenzil,2,3-butanedione, 2,3-pentanedione, 2,3-hexanedione, 3,4-hexanedione,2,3-heptanedione, 3,4-heptanedione, 2,3-octanedione,4,5-octanedionefuril, biacetyl, 1,2-cyclohexanedione, 1,2-naphthaquinoneand acenaphthaquinone.

The term “coinitiator” as used herein means an electron donor compound,i.e. a compound capable of donating electrons in a photochemicalprocess. Suitable examples include organic compounds having heteroatomswith electron lone pairs, for example amine compounds.

The optional coinitiator compound according to (d-ii) is preferably anelectron donor which may be selected from the group consisting ofamines, amides, ethers, thioethers, ureas, thioureas, ferrocene,sulfinic acids and their salts, salts of ferrocyanide, ascorbic acid andits salts, dithiocarbamic acid and its salts, salts of xanthates, saltsof ethylene diamine tetraacetic acid and salts of tetraphenylboronicacid. Particularly preferred electron donors contain an electron donoratom such as a nitrogen, oxygen, phosphorus, or sulfur atom, and anabstractable hydrogen atom bonded to a carbon or silicon atom alpha tothe electron donor atom.

More preferably, the coinitiator is an amine compound, even morepreferably a tertiary amine selected from the group consisting oftriethanolamine, 4-N,N-dimethylaminobenzonitrile, methylN,N-dimethylaminobenzoate, ethyl N,N-dimethylaminobenzoate,N,N-dimethylaminoethyl methacrylate and isoamyl4-N,N-dimethylaminobenzoate, N,N-dimethylaniline, N,N-dimethyltoluidine,N,N-diethanoltoluidine, dimethylaminoanisole, 1 or2-dimethylaminonaphthalene. In particular, the tertiary amine isselected from the group consisting of triethanolamine, methyl4-N,N-dimethylaminobenzoate, ethyl 4-N,N-dimethylaminobenzoate,4-N,N-dimethylaminoethyl methacrylate and isoamyl4-N,N-dimethylaminobenzoate.

Furthermore, the photoinitiator system may additionally comprise (d-iii)a polymerization initiator auxiliary substance which is preferablyselected from the group consisting of iodonium-, sulfonium-,phosphonium-, pyridinium salts and aromatic tertiary phosphinecompounds.

The term “polymerization initiator auxiliary substance” refers to amolecule that produces an advantageous chemical change in any of thecomponents of the polymerization initiator system in a photochemicalprocess. For example, the polymerization initiator auxiliary substancemay be selected from the group consisting of iodonium-, sulfonium-,phosphonium-, pyridinium-salts and aromatic tertiary phosphinecompounds.

Iodonium-, sulfonium- or phosphonium-salts are preferably selected fromthe following group:

-   -   (1) an iodonium compound of the following formula (XII):

R¹³—I⁺-R¹⁴A⁻   (XII)

-   -   -   wherein        -   R¹³ and R¹⁴            -   which are independent from each other represent an                organic moiety, and        -   A⁻ is an anion;

    -   (2) a sulfonium compound of the following formula (XIII):

R¹⁵R¹⁶R¹⁷S⁺A⁻   (XIII)

-   -   -   wherein        -   R¹⁵, R¹⁶ and R¹⁷            -   which are independent from each other, represent an                organic moiety or wherein any two of R¹⁵, R¹⁶ and R¹⁷                form a cyclic structure together with the sulfur atom to                which they are bound, and        -   A⁻ is an anion;

    -   (3) a phosphonium compound of the following formula (XIV):

R¹⁸R¹⁹R²⁰P⁺A⁻   (XIV)

-   -   -   wherein        -   R¹⁸, R¹⁹ and R²⁰            -   which are independent from each other, represent an                organic moiety, and        -   A⁻ is an anion; and

    -   (4) a pyridinium salt.

In the iodonium compounds of formula (XII), R¹³ and R¹⁴ preferablyrepresent an aromatic, an aliphatic or an alicyclic group. An aromaticgroup may be a phenyl group. The phenyl group may be substituted by oneor more straight chain or branched alkyl groups having 1 to 6 carbonatoms, straight chain or branched alkoxy groups having 1 to 6 carbonatoms, aromatic groups such as aryl groups or aryloxy groups, alicyclicgroups having 3 to 6 carbon atoms, halogen atoms, hydroxyl groups, oramino groups. The aliphatic group may be a straight chain or branchedalkyl groups having 1 to 6 carbon atoms which may be substituted by oneor more aromatic groups, alicyclic groups having 3 to 6 carbon atoms,halogen atoms, hydroxyl groups or amino groups. An alicyclic group maybe a group having 3 to 6 carbon atoms which may be substituted by one ormore aromatic groups, aliphatic groups, halogen atoms, hydroxyl groupsor amino groups.

According to a preferred embodiment, the iodonium compound of formula(XII) is a diaryl iodonium salt. Examples of useful diary iodonium saltinclude (4-methylphenyl)[4-(2-methylpropyl) phenyl] iodoniumhexafluoroantimonate, include (4-methylphenyl)[4-(2-methylpropyl)phenyl] iodonium tetrafluoroborate, diphenyliodonium (DPI)tetrafluoroborate, di(4-methylphenyl)iodonium (Me2-DPI)tetrafluoroborate, phenyl-4-methylphenyliodonium tetrafluoroborate,di(4-heptylphenyl)iodonium tetrafluoroborate, di(3-nitrophenyl)iodoniumhexafluorophosphate, di(4-chlorophenyl)iodonium hexafluorophosphate,di(naphthyl)iodonium tetrafluoroborate,di(4-trifluoromethylphenyl)iodonium tetrafluoroborate, DPIhexafluorophosphate, Me2-DPI hexafluorophosphate; DPIhexafluoroarsenate, di(4-phenoxyphenyl)iodonium tetrafluoroborat,phenyl-2-thienyliodonium hexafluorophosphate,3,5-dimethylpyrazolyl-4-phenyliodonium hexafluorophosphate, DPIhexafluoroantimonate, 2,2′-DPI tetrafluoroborate,di(2,4-dichlorophenyl)iodonium hexafluorophosphate,di(4-bromophenyl)iodonium hexafluorophosphate,di(4-methoxyphenyl)iodonium hexafluorophosphate,di(3-carboxyphenyl)iodonium hexafluorophosphate,di(3-methoxycarbonylphenyl)iodonium hexafluorophosphate,di(3-methoxysulfonylphenyl)iodonium hexafluorophosphate,di(4-acetamidophenyl)iodonium hexafluorophosphate,di(2-benzothienyl)iodonium hexafluorophosphate, and DPIhexafluorophosphate.

Particularly preferred iodonium compounds of formula (XII) includediaryliodonium hexafluorophosphate such as diphenyliodonium (DPI)hexafluorophosphate, di(4-methylphenyl)iodonium (Me2-DPI)hexafluorophosphate, diaryliodonium hexafluoroantimonate,(4-methylphenyl)[4-(2-methylpropyl) phenyl] iodoniumhexafluoroantimonate, (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodoniumhexafluorophosphate (Irgacure® 250, commercial product available fromBASF SE), (4-methylphenyl)[4-(2-methylpropyl) phenyl] iodoniumtetrafluoroborate, 4-octyloxyphenyl phenyliodonium hexafluoroantimonate,4-(2-hydroxytetradecyloxyphenyl)phenyliodonium hexafluoroantimonate, and4-(1-methylethyl)phenyl 4-methylphenyliodoniumtetrakis(pentafluorophenyl)borate.

A preferred sulfonium compound of the formula (XIII) isS-(phenyl)thianthrenium hexafluorophosphate of the following formula:

The phosphonium compound of formula (XIV) may be atetrakis-(hydroxymethyl)-phosphonium (THP) salt or atetrakis-(hydroxymethyl)-phosphonium hydroxide (THPOH) salt, wherein theanion A⁻ is selected from the group consisting of formate, acetate,phosphate, sulphate, fluoride, chloride, bromide and iodide.

In a salt of a compound of any one of formula (XII) to (XIV), the anionmay be an anion selected from halogenides such as chloride, bromide andiodide, hexafluorophosphate, tetrafluoroborate, tetraphenylborate,hexafluoroantimonate and trifluoromethylsulfonate.

Furthermore, the photoinitiator system may additionally comprise anaromatic tertiary phosphine compound, wherein it is preferred that thearomatic tertiary phosphine compound has the following formula (XV):

Z₄—R²¹   (5)

-   -   wherein    -   Z₄ is a group of the following formula (6)

R²²(Ar)P—   (6)

-   -   -   wherein        -   R²² represents a substituted or unsubstituted hydrocarbyl            group;        -   Ar represents a substituted or unsubstituted aryl or            heteroaryl group;

    -   R²¹ is a substituted or unsubstituted hydrocarbyl group or a        group        -   L₃Z₄′, wherein        -   L₃ is a substituted or unsubstituted divalent hydrocarbyl            group which may contain a linkage selected from an ether            linkage, a thioether linkage, an ester linkage, an amide            linkage, and a urethane linkage and        -   Z₄′ has the same meaning as Z₄, whereby Z₄ and Z₄′ may be            the same or different;

wherein the group R²² and Ar may be substituted by one or more groupsselected from a hydroxyl group, an oxo group, a —NR²³R²⁴ group (whereinR²³ and R²⁴, which may be the same or different, are selected from ahydrogen atom and C₁₋₆ alkyl groups), a carboxyl group, and a grouphaving a polymerizable double bond, and

R²¹ and L₃ may be substituted by one or more groups selected from ahydroxyl group, an oxo group, a —NR²⁵R²⁶ group (wherein R²⁵ and R²⁶,which may be the same or different, are selected from a hydrogen atomand C₁₋₆ alkyl groups), a carboxyl group, and a group having apolymerizable double bond.

In the aromatic tertiary phosphine compound of the formula (XV),moieties Z₄, R²¹, Ar, R²² and L₃ may be defined as follows:

For R²², the monovalent hydrocarbyl group may be an alkyl group, acycloalkyl group, a cycloalkylalkyl group, an arylalkyl group or an arylgroup.

Ar represents a substituted or unsubstituted aryl or heteroaryl group.An aryl group may be selected from a phenyl group, a naphtyl group, atolyl group, a xylyl group, and a styryl group. A heteroaryl group maybe a pyridyl group.

L₃ is a substituted or unsubstituted divalent hydrocarbyl group whichmay contain a linkage selected from an ether linkage, a thioetherlinkage, an ester linkage, an amide linkage, and a urethane linkage. ForL₃, the divalent hydrocarbyl group may be an alkyldiyl group, acycloalkyldiyl group, a cycloalkylalkyl-diyl group, an arylalkyl-diylgroup or an aryldiyl group. In a cycloalkylalkyl-diyl, one valency maybe bonded to each of the cycloalkyl moiety or the alkyl moiety, or bothvalencies may be bonded to either the cycloalkyl moiety or the alkylmoiety. In a arylalkyl-diyl group, each of the aryl moiety or the alkylmoiety may be monovalent respectively, or either the aryl moiety or thealkyl moiety is divalent, while the other moiety is nonvalent. In acycloalkylalkyl-diyl, each of the cycloalkyl moiety or the alkyl moietymay be monovalent respectively, or either the cycloalkyl moiety or thealkyl moiety is divalent, while the other moiety is nonvalent.

The following definitions apply both for the monovalent and the divalenthydrocarbyl group, therefore, for the definition of the divalenthydrocarbyl group, the suffixes “diyl” and “-diyl” are bracketed.

An alkyl(diyl) group may be straight-chain or branched C₁₋₂₀ alkyl(diyl)group, typically a C₁₋₈ alkyl(diyl) group. Examples for a C₁₋₆alkyl(diyl) group can include linear or branched alkyl(diyl) groupshaving 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, for example,methyl(diyl), ethyl(diyl), n-propyl(diyl), isopropyl(diyl),n-butyl(diyl), isobutyl(diyl), sec-butyl(diyl), tert-butyl(diyl),n-pentyl(diyl), isopentyl(diyl) and n-hexyl(diyl).

A cycloalkyl(diyl) group may be a C₃₋₂₀ cycloalkyl(diyl) group. Examplesof the cycloalkyl(diyl) group can include those having 3 to 14 carbonatoms, for example, cyclopropyl(diyl), cyclobutyl(diyl),cyclopentyl(diyl) and cyclohexyl(diyl). A cycloalkylalkyl(diyl) groupcan include those having 4 to 20 carbon atoms.

A cycloalkylalkyl(-diyl) group can include a combination of a linear orbranched alkyl(diyl) group having 1 to 6 carbon atoms and acycloalkyl(diyl) group having 3 to 14 carbon atoms. Examples of thecycloalkylalkyl(-diyl) group can for example, includemethylcyclopropyl(-diyl) methylcyclobutyl(-diyl),methylcyclopentyl(-diyl), methylcyclohexyl(-diyl),ethylcyclopropyl(-diyl), ethylcyclobutyl(-diyl),ethylcyclopentyl(-diyl), ethylcyclohexyl(-diyl),propylcyclopropyl(-diyl), propylcyclobutyl(-diyl),propylcyclopentyl(-diyl), propylcyclohexyl(-diyl).

An arylalkyl(-diyl) group may be a C₇₋₂₀ arylalkyl(-diyl) group,typically a combination of a linear or branched alkyl(diyl) group having1 to 6 carbon atoms and an aryl(-diyl) group having 6 to 10 carbonatoms. Specific examples of an arylalkyl(-diyl) group are abenzyl(-diyl) group or a phenylethyl(-diyl) group.

An aryl(diyl) group can include aryl(diyl) groups having 6 to 10 carbonatoms. Examples of the aryl(diyl) group are phenyl(diyl) andnaphtyl(diyl). Aryl(diyl) groups may contain 1 to 3 substituents.Examples of such substituents can include halogen atoms, a cyano group,a hydroxy group, an amino group, C₁₋₆ alkyl groups and C₁₋₆ alkoxygroups. Here, illustrative of the halogen atoms can be fluorine,chlorine, bromine and iodine. The C₁₋₄ alkyl(diyl) groups are, forexample, methyl(diyl), ethyl(diyl), n-propyl(diyl), isopropyl(diyl) andn-butyl(diyl). Illustrative of the C₁₋₄ alkoxy(diyl) groups are, forexample, methoxy(diyl), ethoxy(diyl) and propoxy(diyl). The alkyl(diyl)moieties in these substituents may be linear, branched or cyclic.

Preferably, the hydrocarbyl group is an aryl(diyl) group selected from aphenyl(diyl) group and a naphthyl(diyl) group, which groups mayoptionally be substituted by one to three groups selected from halogenatoms, a cyano group, an amino group, a hydroxy group, C₁₋₆ alkyl groupsand C₁₋₆ alkoxy groups, or wherein the hydrocarbyl group is anon-aromatic hydrocarbyl group selected from a straight chain orbranched alkyl group, a straight chain or branched alkenyl group, or astraight chain or branched alkynyl group.

The C₁₋₈ alkyl(diyl) group and the C₃₋₁₄ cycloalkyl(diyl) group mayoptionally be substituted by one or more members of the group selectedfrom a C₁₋₄ alkyl group, C₁₋₄ alkoxy group, a phenyl group, and ahydroxy group. Examples for a C₁₋₄ alkyl group can include linear orbranched alkyl groups having 1 to 4 carbon atoms, for example, methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl.Examples for an C₁₋₄ alkoxy group can include linear or branched alkoxygroups having 1 to 4 carbon atoms, for example, methoxy, ethoxy,n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, and tert-butoxy.

Moreover, in formula (XV), any of the hydrocarbyl group may besubstituted by one or more groups selected from halogen atoms, a cyanogroup, an amino group or a hydroxy group.

Accordingly, in the hydrocarbyl groups some or all hydrogen atoms arereplaced by halogen atoms (e.g., fluoro, bromo, chloro), for example,halo-substituted alkyl groups such as chloromethyl, chloropropyl,bromoethyl and trifluoropropyl, and cyanoethyl.

In case the hydrocarbyl group contains an alkyl(diyl) chain, one or morecarbon atoms in the alkyl(diyl) chain may be replaced by an oxygen atom,a sulfur atom, an amide group, an ester group, or a urethane group. Incase the hydrocarbyl group is an alkyl group having more than one carbonatom, the alkyl group contains an alkylene. Accordingly, in case thehydrocarbyl group is an n-hexyl group, any of the carbon atoms of thealkylene chain excluding the terminal methyl group may be replaced by anoxygen atom, a sulfur atom, an amide group, an ester group, a urethanegroup or an NH group. Therefore, the following groups may be given asspecific examples in case of one or more oxygen atoms:

In formula (XV), group R²² and/or Ar as well as R²¹ and/or L₃ may besubstituted with a polymerizable double bond, preferably a carbon-carbondouble bond. Examples of polymerizable carbon-carbon double bondsinclude vinyl, conjugated vinyl, allyl, acryl, methacryl and styryl.Preferably, the polymerizable double bond is selected from the groupconsisting of methacryl, acryl and styryl. More preferably, the doublebond is styryl.

Preferably, R²⁶ and Ar independently are aromatic hydrocarbyl groupsselected from a phenyl group, a naphtyl group, a tolyl group, a xylylgroup, and a styryl group.

As regards R²¹, this moiety is preferably an aryl group, which may besubstituted by one or more groups selected from a hydroxyl group, anamino group, a —NR²⁵R²⁶ group (wherein R²⁵ and R²⁶, which may be thesame or different, are selected from C₁₋₆ alkyl groups), a carboxylgroup, and a group having a polymerizable double bond. Alternatively,R²¹ is preferably a group L₃Z₄′ wherein Z₄′ and Z₄ are the same.

More preferably, R²¹ is a C₁₋₆ alkyl group or a C₁₋₆ alkenyl group,which groups may be substituted by one or more groups selected from ahydroxyl group, an amino group, a —NR²⁵R²⁶ group (wherein R²⁵ and R²⁶,which may be the same or different, are selected from C₁₋₆ alkylgroups), a carboxyl group, and a group having a polymerizable doublebond. The group having a polymerizable double bond may be vinyl group,an allyl group, a (meth)acryloyloxy group or a (meth) acryloylamidogroup.

Even more preferably, the aromatic phosphine compound is a compound offormula (XV) wherein Z₄ is a group of the following formula:

Specific examples for a compound of formula (XV) include triphenylphosphine (TPP), 4-(diphenylphosphino)styrene (DPPS),4-(diphenylphosphino)benzoic acid, 4-(diphenylphosphino) benzoic acid,3-(diphenylphophonino)propionic acid, (4-(diphenylphosphino)N,N′-dimethylaniline, 2,2′-bis(diphenylphosphino)benzophenone (BDPPEP),bis[2-(diphenylphosphino)phenyl]ether (BDPPE),(4-Hydroxyphenyl)diphenylphosphine, allyldiphenylphosphine. Preferably,the compound of formula (XV) is triphenyl phosphine (TPP) or4-(diphenylphosphino)styrene (DPPS), more preferably4-(diphenylphosphino)styrene (DPPS).

According to (e), the aqueous dental composition comprises a stabilizer.The aqueous dental composition may comprise one or more stabilizer(s) ofthe formula (VII) and/or (VIII).

The term “stabilizer” as used herein means any compound capable ofpreventing polymerizable compounds contained in the aqueous dentalcomposition from spontaneous polymerization during storage. However, thestabilizer does not disturb or prevent intended polymerisation curing ofthe aqueous dental composition during application.

Preferably, the stabilizer is a compound of the following formula (VII)and/or (VIII):

-   -   wherein    -   the R³, which may be the same or different, independently        represent a branched C₃₋₈ alkyl group or alkenyl or a C₃₋₈        cycloalkyl or cycloalkenyl group,    -   R⁴ represents a hydrogen atom, C₁₋₆ alkyl or C₂₋₆ alkenyl group,        or a C₁₋₆ fluoroalkyl or C₂₋₆ fluoroalkenyl group,    -   X represents a group selected from a C₁₋₈ alkyl group or a C₃₋₈        cycloalkyl group, and    -   n is 0, 1 or 2.

It was surprisingly found that the class of stabilizers of formula (VII)and/or (VIII) provides for full or at least substantial avoidance ofdiscoloration upon storage and/or during photocuring. In particular,this class of stabilizers provides for a surprising stabilizing effectin an acidic aqueous mixture so that an aqueous dental compositionhaving a pH of at most 7 may be provided which has no or substantiallyno discoloration upon storage and an excellent storage stability due toan improved resistance against premature polymerization.

More preferably, the stabilizer is a compound of formula (VII) and/or(VIII) wherein the R³, which may be the same or different, independentlyrepresent a branched C₃₋₈ alkyl group or a C₃₋₈ cycloalkyl group, and R⁴represents hydrogen atom, a C₁₋₆ alkyl group or a C₁₋₆ fluoroalkylgroup, and n is 0 or 1. Even more preferably, the stabilizer is acompound of formula (VII) and/or (VIII) wherein the R³, which may be thesame or different, independently represent a branched C₃₋₈ alkyl groupand R⁴ represents hydrogen atom or a C₁₋₆ alkyl group, and n is 0. Mostpreferably, the stabilizer is a compound of the following formulae(VIIa), (VIIb) or (VIIa):

wherein R_(3′), R_(3″), R_(3′″), R_(3*), R_(3**) and R_(3***), which maybe the same or different, independently represent a methyl or an ethylgroup. It is particularly preferred that the stabilizer of formulae(VIIa), (VIIb) or (VIIIa) is a compound of the following formulae:

preferably DTBHQ.

2,5-di-tert-butyl-hydroquinone (DTBHQ),2,5-di-tert-butyl-4-methoxyphenol and 2,5-di-tert-butyl-benzoquinone(DTBBQ) are commercially available standard chemicals. In general,monoether compounds of formula (VII) such as2,5-di-tert-butyl-hydroquinone monoalkylethers of formula (VIb) may bereadily obtained from a dihydroquinone of formula (VII), such as DTBHQ,as starting material by means of selective monoetherification catalyzedin the presence of NaNO₂ in combination with an inorganic acid suchH₂SO₄ or a solid acidic catalyst such as a styrene based sulfonatedpolymer, e.g. the commercially available ion exchange resins Amberlyst®15 and Aberlite® IR120, analogously as described by C. Gambarotti et al.in Current Organic Chemistry 2013, 17, pages 1108 to 1113.Alternatively, monoether compounds of formula (VII) such as2,5-di-tert-butyl-hydroquinone monoalkylethers of formula (VIb) may beobtained by reacting a dihydroquinone of formula (VII), such as DTBHQ,with an alkyl alcohol in the presence of a transition metal saltselected from copper and iron salts analogously as described in the U.S.Pat. No. 4,469,897.

The stabilizer DTBHQ is particularly preferred, since from the presentexperimental Example it appears that this stabilizer provides the bestresults in view of the discoloration problematic, i.e. there is no oralmost no discoloration of the aqueous dental composition upon storageat 50° C. for 30 days, or at 60° C. or 70° C. for at least 3 days.

Discoloration upon storage and/or during photocuring may be determinedaccording to ISO 7491:2000(en).

The aqueous dental composition according to the invention contains thestabilizer in an amount of 0.001 to 1 percent by weight, preferably0.005 to 0.8 percent by weight based on the total weight of thecomposition. When the amount of the stabilizer (iii) is below the aboveindicated lower limit of 0.001, then storage stability of the aqueousdental composition might be insufficient, since the amount of stabilizeris too small to provide a stabilizing effect. However, when the amountof stabilizer (iii) is above the maximum threshold of 1 percent byweight, then the applicability of the aqueous dental composition mightbe negatively affected, since higher amounts of stabilizer may disturbor even substantially prevent intended polymerisation curing of theaqueous dental composition during application.

According to (f), the aqueous dental composition of the presentinvention comprises a solvent mixture comprising water and an organicsolvent. The solvent mixture may comprise one or more organicsolvent(s).

The term “organic solvent” as used herein means any organic compoundwhich is fluid or liquid at room temperature and which is capable ofdissolving or at least partly dissolving the components according to(a), (b), (c), (d) and (e) of the present aqueous dental composition.The organic solvent is suitably selected in view of its volatility andphysiological harmlessness. Preferably, the organic solvent is morevolatile than water, that is it has a vapour pressure higher than waterat 20° C. Besides, it is preferred that the organic solvent is non-toxicfor the patient to be treated, in particular for a human patient.

Preferably, the organic solvent of the solvent mixture is selected fromthe group consisting of n-propanol, iso-propanol, n-butanol,iso-butanol, sec-butanol, tert-butanol, acetone and methyl ethyl ketone.Preferably, the aqueous dental composition comprises the solvent mixturein an amount of 25 to 50 percent by weight, more preferably 27 to 47percent by weight, most preferably 29 to 44 percent by weight based onthe total weight of the aqueous dental composition.

It is preferred that according to (f), the organic solvent comprised inthe solvent mixture is n-propanol or iso-propanol, preferablyiso-propanol.

Preferably, the solvent mixture according to (f) comprises water in anamount of at least 1 percent by weight, more preferably at least 8percent by weight, most preferably at least 16 percent by weight basedon the total weight of the composition.

It is preferred that the sum of the masses of the above describedcomponents (a) to (f) amounts to 100% by weight based on the totalweight of the composition. However, this sum may also amount to lessthan 100%, preferably 90%, more preferably 80%, most preferably 70% byweight based on the total weight of the composition.

The remaining part of the aqueous dental composition having a pH of atmost 7 which sum of components (a) to (f) amounts to less than 100% byweight based on the total weight of the composition may be constitutedby further components. Such further components may be, for example, apolymerizable monomer having at least three polymerizable double bonds,a polymerizable monomer having one or two polymerizable double bonds anda particulate filler, which are described in the following.

The aqueous dental composition according to the invention may furthercomprise one or more polymerizable monomer(s) having at least threepolymerizable double bonds.

Preferably, the polymerizable monomer having at least threepolymerizable double bonds is selected from the group consisting oftrimethylolethane triacrylate, trimethylolethane trimethacrylate,trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, andtri- and tetra-acrylates and methacrylates of pentaerythritol anddipentaerythritol.

Besides, the aqueous dental composition according to the presentinvention may further comprise one or more polymerizable monomerspreferably having one or two polymerizable double bond(s).

Preferably, the one or more polymerizable monomer(s) having one or twopolymerizable double bond(s) is/are selected from the group consistingof (meth)acrylate compound(s), N-substituted or N-unsubstituted alkylacrylic or acrylic acid amide compound(s), mono-, bis- or poly(meth)acrylamides and bis(meth)acrylamide compounds. More preferably, the oneor more polymerizable monomers having a polymerizable double bondincludes a (meth)acrylamide, a (meth)acrylic acid ester and/or abis(meth)acrylamide compound.

The (meth)acrylate compound may be selected from the group of methylacrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate,propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropylmethacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate(HEMA), hydroxypropyl acrylate, hydroxypropyl methacrylate,tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, glycidylacrylate, glycidyl methacrylate, the diglycidyl methacrylate ofbis-phenol A (“bis-GMA”), glycerol mono- and di-acrylate, glycerol mono-and dimethacrylate, ethyleneglycol diacrylate, ethyleneglycoldimethacrylate, polyethyleneglycol diacrylate (where the number ofrepeating ethylene oxide units vary from 2 to 30), polyethyleneglycoldimethacrylate (where the number of repeating ethylene oxide units varyfrom 2 to 30 especially triethylene glycol dimethacrylate (TEGDMA),neopentyl glycol diacrylate, neopentylglycol dimethacrylate,1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate,1,4-butanedioldiacrylate, 1,4-butanediol dimethacrylate, 1,6-hexane dioldiacrylate, 1,6-hexanediol dimethacrylate, di-2-methacryloyloxethylhexamethylene dicarbamate, di-2-methacryloyloxyethyltrimethylhexanethylene dicarbamate, di-2-methacryloyl oxyethyldimethylbenzene dicarbamate,methylene-bis-2-methacryloxyethyl-4-cyclohexyl carbamate,di-2-methacryloxyethyl-dimethylcyclohexane dicarbamate,methylene-bis-2-methacryloxyethyl-4-cyclohexyl carbamate,di-1-methyl-2-methacryloxyethyl-trimethyl-hexamethylene dicarbamate,di-1-methyl-2-methacryloxyethyl-dimethylbenzene dicarbamate,di-1-methyl-2-methacryloxyethyl-dimethylcyclohexane dicarbamate,methylene-bis-1-methyl-2-methacryloxyethyl-4-cyclohexyl carbamate,di-1-chloromethyl-2-methacryloxyethyl-hexamethylene dicarbamate,di-1-chloromethyl-2-methacryloxyethyl-trimethylhexamethylenedicarbamate, di-1-chloromethyl-2-methacryloxyethyl-dimethylbenzenedicarbamate, di-1-chloromethyl-2-methacryloxyethyl-dimethylcyclohexanedicarbamate, methylene-bis-2-methacryloxyethyl-4-cyclohexyl carbamate,di-1-methyl-2-methacryloxyethyl-hexamethylene dicarbamate,di-1-methyl-2-methacryloxyethyl-trimethylhexamethylene dicarbamate,di-1-methy-2-methacryloxyethyl-dimethylbenzene dicarbamate,di-1-methyl-2-metha-cryloxyethyl-dimethylcyclohexane dicarbamate,methylene-bis-1-methyl-2-methacryloxyethyl-4-cyclohexyl carbamate,di-1-chloromethyl-2-methacryloxyethyl-hexamethylene dicarbamate,di-1-chloromethyl-2-methacryloxyethyl-trimethylhexamethylenedicarbamate, di-1-chloromethyl-2-methacryloxyethyl-dimethylbenzenedicarbamate, di-1-chloromethyl-2-methacryloxyethyl-dimethylcyclohexanedicarbamate,methylene-bis-1-chloromethyl-2-methacryloxyethyl4-cyclohexyl carbamate,2,2′-bis(4-methacryloxyphenyl)propane, 2,2′bis(4-acryloxyphenyl)propane,2,2′-bis[4(2-hydroxy-3-methacryloxy-phenyl)]propane,2,2′-bis[4(2-hydroxy-3-acryloxy-phenyl)propane,2,2′-bis(4-methacryloxyethoxyphenyl)propane,2,2′-bis(4-acryloxyethoxyphenyl)propane,2,2′-bis(4-methacryloxypropoxyphenyl)propane,2,2′-bis(4-acryloxypropoxyphenyl)propane,2,2′-bis(4-methacryloxydiethoxyphenyl)propane,2,2′-bis(4-acryloxydiethoxyphenyl)propane,2,2′-bis[3(4-phenoxy)-2-hydroxypropane-1-methacrylate]propane, and2,2′-bis[3(4-phenoxy)-2-hydroxypropane-1-acryalte]propane, may bementioned.

The N-substituted alkyl acrylic or acrylic acid amide compound(s) arepreferably characterized by one of the following formulas:

wherein R₂₇, R*₂₇, R*₂₇, R*₂₇ independently represent a hydrogen atom,—COOM, a straight chain or branched C₁ to C₁₈ alkyl group which may besubstituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroarylgroup, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₃ to C₁₈ cycloalkyl groupwhich may be substituted by a C₁₋₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, or a C₅ to C₁₈ arylor C₃ to C₁₈ heteroaryl group which may be substituted by —COOM, —PO₃M,—O—PO₃M₂ or —SO₃M, R₂₈ and R*₂ independently represent a hydrogen atom,a straight chain or branched C₁ to C₁₃ alkyl group or C₂ to C₁₈ alkenylgroup which may be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ arylor C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₃ to C₁₈cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,or a C₅ to C₁₈ aryl or C₃ to C₁₈ heteroaryl group which may besubstituted by —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, R₂₉ represents adivalent substituted or unsubstituted organic residue having from 13 to45 carbon atoms, whereby said organic residue may contain from 1 to 14carbonyl groups or heteroatoms selected from oxygen, nitrogen andsulphur; preferably R₂₉ is a C₁₃ to C₂₈ alkylene group or a C₁₃ to C₂₈alkenylene group, which may contain 1 to 6 carbonyl groups orheteroatoms selected from oxygen, nitrogen and sulfur, and which may besubstituted by a hydroxyl group, a C₆₋₁₄ aryl group, —COOM, —PO₃M,—O—PO₃M₂ or —SO₃M, wherein in said C₁₃ to C₂₈ alkylene group and saidC₁₃ to C₂₈ alkenylene group, from 1 to 6 —CH₂-groups may be replaced bya —N—(C═O)—CR₃₁═CH₂ group wherein R₃₁ is a hydrogen atom or a C₁ to C₁₈alkyl group, a substituted or unsubstituted C₃ to C₁₈ cycloalkyl group,a substituted or unsubstituted C₄ to C₁₈ aryl or heteroaryl group, asubstituted or unsubstituted C₅ to C₁₈ alkylaryl or alkylheteroarylgroup, a substituted or unsubstituted C₇ to C₃₀ aralkyl group, and asubstituted or unsubstituted C₂ to C₄₅ mono-, di- or polyether grouphaving from 1 to 14 oxygen atoms,

R₃₀ represents a saturated di- or multivalent substituted orunsubstituted C₂ to C₁₈ hydrocarbon group, a saturated di- ormultivalent substituted or unsubstituted cyclic C₃ to C₁₈ hydrocarbongroup, a di- or multivalent substituted or unsubstituted C₄ to C₁₈ arylor heteroaryl group, a di- or multivalent substituted or unsubstitutedC₅ to C₁ alkylaryl or alkylheteroaryl group, a di- or multivalentsubstituted or unsubstituted C₇ to C₃₀ aralkyl group, or a di- ormultivalent substituted or unsubstituted C₂ to C₄₅ mono-, di-, orpolyether residue having from 1 to 14 oxygen atoms, and m is an integer,preferably in the range from 1 to 10, wherein M of any one R₂₇, R*₂₇,R*₂₇, R**₂₇, R₂₈, R*₂₈, R₂₉ and R₃₀, which M are independent from eachother, each represent a hydrogen atom or a metal atom.

For R₂₈, R*₂₈ and R₂₉, the term “C₃ to C₁₈ cycloalkyl group” includespolycycloalkyl groups comprising two or more cycloalkyl groups, whereinat least two rings share one C—C bond. Preferred are C₅ to C₁₄polycycloalkyl groups, more preferred are C₈ to C₁₂ polycycloalkylgroups, and most preferred are tricyclo[5.2.1.0^(2,6)]decyl oradamantyl.

In compound of formula (A), R₂₈ and R*₂₈ may cooperatively form a ringin which R₂₈ and R₂₈* are linked by a C—C bond or a functional groupselected from the group consisting of an ether group, a thioether group,an amine group and an amide group.

Mono-, bis- or poly(meth) acrylamide preferably have the followingformulae:

Other suitable examples of polymerizable monomers having a polymerizabledouble bond are isopropenyl oxazoline, vinyl azalactone, vinylpyrrolidone, styrene, divinylbenzene, urethane acrylates ormethacrylates, epoxy acrylates or methacrylates and polyol acrylates ormethacrylates.

It is preferred to select the above described polymerizable monomerswith the proviso that they do not contain ester groups, or at least onlyester groups which do not hydrolyze in aqueous media at pH 3 at roomtemperature within one month. Thereby, an advantageous stability of theaqueous dental composition having a pH of at most 7 in terms ofshelf-life stability of the uncured dental composition as well asstability after curing in the mouth of a patient is ensured.

Preferably, the aqueous dental composition according to the presentinvention further comprises a particulate filler. The aqueous dentalcomposition may comprise one or more particulate filler(s). The aqueousdental composition of the present invention may preferably comprise theparticulate filler in an amount of 0.1 to 80 percent by weight based onthe total weight of the composition.

The particulate filler may be in inorganic or organic form or a mixtureof at least two components selected from inorganic and organiccomponent. The particulate filler may in the form of a reactive ornon-reactive filler.

Suitable particulate fillers may be selected from fillers currently usedin dental compositions. The filler should be finely divided andpreferably has a maximum particle diameter less than about 100 μm and anaverage particle diameter less than about 10 μm. The filler may have aunimodal or polymodal (e.g., bimodal) particle size distribution. Theparticle size may be measured, for example, by electron microscopy or byusing a conventional laser diffraction particle sizing method asembodied by a MALVERN Mastersizer S or MALVERN Mastersizer 3000apparatus. The particulate filler may be a multimodal particulatenon-reactive filler representing a mixture of two or more particulatefractions having different average particle sizes. The particulatereactive filler may also be a mixture of particles of different chemicalcomposition. The particulate non-reactive filler may be surface modifiedby a surface modifying agent.

The filler can be an inorganic material. It can also be a crosslinkedorganic material that is insoluble in the polymerizable resin, and isoptionally filled with inorganic filler. The filler can be radiopaque.Examples of suitable particulate inorganic fillers arenaturally-occurring or synthetic materials such as quartz, nitrides suchas silicon nitride, glasses derived from, for example Ce, Sb, Sn, Zr,Sr, Ba and Al, colloidal silica, feldspar, borosilicate glass, kaolin,talc, titania, and zinc glass, and submicron silica particles such aspyrogenic silicas.

Examples of suitable non-reactive organic filler particles includefilled or unfilled pulverized polycarbonates or polyepoxides. Preferablythe surface of the filler particles is treated with a coupling agent inorder to enhance the bond between the filler and the matrix. The use ofsuitable coupling agents includegamma-methacryloxypropyltrimethoxysilane,gamma-mercaptopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane,and the like.

The particulate filler may also be a filler obtainable by a process forthe preparation of composite filler particles, comprising:

1) coating a particulate filler having a median particle size (D50) offrom 1 to 1200 nm with a coating composition containing a film-formingagent forming a coating layer on the surface of the particulate filler,said coating layer displaying reactive groups on the surface of thecoating layer, said reactive groups being selected from additionpolymerizable groups and step-growth polymerizable groups, therebyforming a coated particulate filler; subsequently or concurrently

2) agglomerating the coated particulate filler, optionally in thepresence of a further crosslinking agent and optionally in the presenceof a further particulate filler not displaying reactive groups, forproviding a granulation of the coated particulate filler wherein thegranulation contains the coated particulate filler particles and theoptional further particulate filler particles separated from andconnected to each other by at least one coating layer, whereby the atleast one coating layer may be crosslinked by crosslinking groupsobtained by reacting the reactive groups and optionally a furthercrosslinking agent;

3) optionally milling, classifying and/or sieving the granulation of thecoated particulate filler; and

4) optionally further crosslinking the granulation of the coatedparticulate filler; for providing composite filler particles having amedian particle size (D50) of from 1 to 70 μm, wherein reactive groupsare transformed into crosslinking groups obtained by reacting reactivegroups and optionally a further crosslinking agent, and wherein theparticulate filler is the main component by volume of the compositefiller particles as further described in EP-A 2 604 247.

Preferably, the aqueous dental composition according to the presentinvention comprises a reactive particulate glass as particulate filler.

The term “reactive particulate glass” means a solid mixture of metaloxides, wherein the mixture is in particulate form. Specific examples ofparticulate reactive fillers are selected from calcium alumino silicateglass, calcium alumino fluorosilicate glass, calciumaluminumfluoroborosilicate glass, strontium aluminosilicate glass,strontium aluminofluorosilicate glass, strontiumaluminofluoroborosilicate glass. Suitable particulate reactive fillersmay be in the form of metal oxides such as zinc oxide and/or magnesiumoxide, and/or in the form of ion-leachable glasses, e.g., as describedin U.S. Pat. Nos. 3,655,605, 3,814,717, 4,143,018, 4,209,434, 4,360,605and 4,376,835.

Preferably, the reactive particulate glass is a reactive particulateglass comprising:

-   -   1) 20 to 45% by weight of silica,    -   2) 20 to 40% by weight of alumina,    -   3) 20 to 40% by weight of strontium oxide,    -   4) 1 to 10% by weight of P₂O₅, and    -   5) 3 to 25% by weight of fluoride.

Furthermore, it is preferred that the present dental compositioncomprises 0.1 to 80, preferably 0.5 to 60, more preferably 1 to 40percent by weight of the reactive particulate glass, based on the weightof the entire weight of the aqueous dental composition.

The reactive particulate glass usually has an average particle size offrom 0.005 to 100 μm, preferably of from 0.01 to 40 μm as measured, forexample, by electron microscopy or by using a conventional laserdiffraction particle sizing method as embodied by a MALVERN MastersizerS or MALVERN Mastersizer 3000 apparatus.

The reactive particulate glass may be surface modified by a surfacemodifying agent.

Preferably, the surface modifying agent is a silane. A silane provides asuitable hydrophobicity to the reactive particulate glass, which allowsfor an advantageous, homogeneous admixture with the organic componentsof the present aqueous dental composition.

Furthermore, it is preferred to include non-reactive fillers in thepresent aqueous dental composition for changing the appearance of thecomposition, for controlling viscosity of the composition, for furtherimproving mechanical strength of a dental glass ionomer cement obtainedfrom the composition, and e.g. for imparting radiopacity. Thenon-reactive filler should be non-toxic and suitable for use in themouth.

The filler may be in the form of an inorganic material. It can also be acrosslinked organic material that is insoluble in the polymerizablepolymer according to (B) comprised in the present aqueous dental glassionomer composition, and is optionally filled with inorganic filler.

For example, suitable non-reactive inorganic fillers may be quartz,nitrides such as silicon nitride, colloidal silica, submicron silicasuch as pyrogenic silicas, colloidal zirconia, feldspar, borosilicateglass, kaolin, talc or a metallic powder comprising one or more metalsor metal alloys.

Examples of suitable non-reactive organic fillers include filled orunfilled particulate polycarbonates or polyepoxides. Preferably thesurface of the non-reactive organic filler particles is treated with acoupling agent in order to enhance the bond between the filler and thematrix. Suitable coupling agents include silane compounds such asgamma-methacryloxypropyltrimethoxysilane,gamma-mercaptopropyltriethoxysilane andgamma-aminopropyltrimethoxysilane.

According to a particularly preferred embodiment, the aqueous dentalcomposition having a pH of at most 7 comprises:

-   -   (a) 20 to 60 percent by weight based on the total weight of the        composition of a polymerizable compound of the following formula        (I):

A-L-B  (I)

-   -   -   wherein        -   A is a group of the following formula (III)

-   -   -   -   X¹ is CO or CH₂;            -   R¹ is a hydrogen atom,            -   R² is a hydrogen atom, a methyl group or —CH₂—COOM,                preferably X¹ is CO and R² is a hydrogen atom or a                methyl group, more preferably X¹ is CO and R² is a                hydrogen atom,

        -   L is a divalent C₂₋₁₂ alkenylene linker group, which may            contain 1 to 3 carbonyl groups or nitrogen atom(s), and            which may be substituted by a hydroxyl group, preferably L            is an unsubstituted divalent C₃₋₈ alkenylene linker group,            more preferably L is —CH₂—CH═CH—CH₂—;

        -   B is a group according to the definition of A,

    -   (b) 3 to 15 percent by weight based on the total weight of the        composition of a polymerizable compound of the following formula        (V):

A′-L′-A′   (V)

-   -   -   wherein the        -   A′ which are independent from each other, each represent a            group of the following formula (VI)

-   -   -   -   wherein            -   X²* is CO,            -   R¹* is a hydrogen atom,            -   R²* is a hydrogen atom,            -   R* is an ethyl group,

        -   L′ is a divalent C₂₋₁₂ alkylene linker group, which may            contain 1 to 3 carbonyl groups or nitrogen atom(s), and            which may be substituted by a hydroxyl group, preferably L′            is an unsubstituted divalent C₂₋₈ alkylene linker group,            more preferably L′ is n-propylene;

    -   (c) 1 to 20 percent by weight based on the total weight of the        composition of a polymerizable monomer having one or more acidic        groups, preferably a polymerizable phosphoric acid ester of        formula (IX);        -   (d) 0.001 to 5 percent by weight based on the total weight            of the composition of a photoinitiator system; preferably,            the photoinitiator system comprises a 1,2-diketone            photoinitiator compound having a light absorption maximum in            the range from 300 to 500 nm

    -   (e) 0.001 to 1 percent by weight based on the total weight of        the composition of a stabilizer of formula (VII) and/or (VIII);        and

    -   (f) 25 to 50 percent by weight based on the total weight of the        composition of a solvent mixture comprising water and an organic        solvent selected the group consisting of ethanol, n-propanol,        iso-propanol, n-butanol, iso-butanol, sec-butanol, tert-butanol,        acetone and methyl ethyl ketone; preferably the organic solvent        is n-propanol or iso-propanol, more preferably iso-propanol.

A composition comprising at least a) a polymerizable compound of theformula (I) and b) a polymerizable compound of the formula (V) may beused for the preparation of an aqueous dental composition, preferably anaqueous dental composition having a pH of at most 7.

For this use, the compounds of formulae (I) and (V) as defined above forthe aqueous dental composition having a pH of at most 7 according toclaim 1 may be used alone or in combination with any components suitablefor the preparation of a dental composition. Preferably, compounds offormulae (I) and (V) are used alone or in combination with at least oneof components c), d), e) and f) defined for the aqueous compositionhaving a pH of at most 7 and optionally with further componentsdescribed above for the aqueous composition having a pH of at most 7.

The invention will now be further illustrated with reference to thefollowing examples.

EXAMPLES

Introductory remarks concerning wetting characteristics and viscosityWetting is a complex, time dependent process strongly affected by thesurface roughness and the nature of material surface. In a firstapproximation, the behavior of a liquid (L) on a solid surface (S) maybe described by the following parameters: surface free energy of thesolid as (SFE), surface tension of the liquid σ_(L) (ST), tension on theliquid/solid interface σ_(L/S) (IT) and the contact angle ϑ (CA) at theternary liquid/solid (L/S) towards gas/vapour (V) interface. SFE, ST andIT are area-related energy values [mN*m⁻¹]. CA can be positive only withvalues between 0° and 180°.

As a simple analysis, the static sessile drop method may be used.Accordingly, the ternary L/S/V interface is observed after anequilibrium time t at its equilibrium state forming the static contactangle s. The relationship of the parameters is given by YOUNG'sequation:

cos ϑ_(S)=(σ_(S)−σ_(L/S))*σ_(L) ⁻¹

The capability of the present aqueous dental composition to efficientlywet a tooth surface may be expressed by the static ϑ_(S) (sCA). Formeasurement of the sCA, the three phases of the ternary system L, S andV are as follows: S is a planar or structured tooth surface or any solidsurface having a SFE similar to that of a tooth surface, L is thepresent aqueous dental composition having a pH of at most 7, and V isambient air. On structured solid surfaces S such as enamel and dentin, asuitable scaling factor of the sCA may be introduced.

The static sessile drop measurement was carried out with a OCA-15Egoniometer from DataPhysics Instruments, Filderstadt, Germany, whereinSCA20 software from DataPhysics Instruments was used for measurementanalysis.

According to the present invention, for an advantageous surfacewettability, the sCA as is preferably less than 25°, more preferablyless than 10⁰, most preferably less than 5°.

The ST of the liquid, aqueous dental composition σ_(L) allows for apreliminary assessment whether or not the liquid aqueous dentalcomposition might provide for a suitable wetting of the structured toothsurface. This is because the SFE in the form of the tooth surface asremains unchanged at a defined humidity level. As can be gathered fromthe YOUNG'S equation, while lowering as provides for a higher value forcos as, the degree value for sCA becomes lower. Hence, once a suitablewetting providing an at least sufficiently low sCA is obtained,measurement of σ_(L) provides for an uncomplicated pretesting whether ornot the present aqueous dental composition may provide suitable surfacewetting characteristics.

For quantification of the wettability, the contact angle as may bemeasured, preferably by the static sessile drop method described above.

ST σ_(L) may be determined by means of any prior art determinationmethod. For example, the value of σ_(L) may be determined by WASHBURNCapillary Rise method, WILHELMY Plate or DU NOÜY Ring method, MaximumBubble Pressure method, Pendant or Sessile Drop method, Drop Weight orVolume method and Spinning Drop method. The aforementioned methods aree.g. described in J. G. WEBSTER, “Mechanical VariablesMeasurement—Solid, Fluid, and Thermal”, CRC Press Inc., 1999, p. 12-1 to12-13.

In the present invention, ST σ_(L) was determined by the Pendant Dropmethod using an OCA-15E goniometer from DataPhysics Instruments,Filderstadt, Germany, wherein SCA20 software from DataPhysicsInstruments was used for measurement analysis.

According to the present invention, the surface tension ST of theliquid, aqueous dental composition σ_(L) is preferably within a range offrom 5 to 75 mN*m⁻¹, more preferably 10 to 50 mN*m⁻¹, and in particular10 to 40 mN*m⁻¹.

Furthermore, an important parameter interrelating with sCA as and ST GLis the penetration coefficient (k_(P)), which is defined as follows:

k _(P)=σ_(L)* cos ϑ_(S)*(2η)⁻¹

wherein η is the viscosity of the aqueous dental composition.

The penetration coefficient k is a measure of the ability of a liquidsuch as the aqueous dental composition to penetrate into a capillaryspace such as pores or cavities of the tooth surface or gingivalpockets. From the above equation for k_(P), it is understood that thehigher the viscosity η, the lower k_(P) becomes. Hence, not only in viewof workability and handling comfort of the aqueous dental composition,but also in view of suitable penetration of the tooth surface, it isimportant to suitably set the viscosity as of the aqueous dentalcomposition.

The viscosity was determined using a Kinexus pro+ rotation typerheometer from Malvern Instruments Ltd, Worcestershire, UK.

According to the present invention, the viscosity of the aqueous dentalcomposition r is preferably set within a range of from 1 to 100 mPa*smore preferably 5 to 75 mPa*s, and in particular 10 to 50 mPa*s.

Preparation of Aqueous Dental Compositions

Eight different aqueous dental compositions 1 to 8 representing aqueousdental compositions according to the invention have been prepared byadmixing the components listed in Table 1.

TABLE 1 Aqueous dental compositions 1 to 8 Aqueous dental composition: 12 3 4 5 6 7 8 PENTA 0.0 6.5 6.5 4.4 6.5 0.5 5.0 5.0 [wt.-%] BAABE 44.447.4 7.3 41.9 20.0 45.4 46.4 46.4 [wt.-%] BADEP 3.9 5.4 20.0 3.5 7.3 7.54.4 4.4 [wt.-%] MDP 11.0 0.0 13.0 9.5 13.0 0.5 9.5 9.5 [wt.-%]Propan-2-ol 16.5 16.5 20.0 16.5 20.0 19.0 5.0 26.5 [wt.-%] Water 21.021.0 30.0 21.0 30.0 23.9 26.5 5.0 [wt.-%] CQ 1.8 1.8 1.8 1.8 1.8 1.8 1.81.8 [wt.-%] DMABN 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 [wt.-%] BMIHP 0.7 0.70.7 0.7 0.7 0.7 0.7 0.7 [wt.-%] DTBHQ 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1[wt.-%] Sum 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 [wt.-%] Listof abbreviations used in Table 1: PENTA: Dipentaerythritol pentacrylatephosphate BAABE: N,N′-(2E)-but-2-en-1,4-diallylbis-[(N-prop-2-en-l)amide BADEP: N,N′-Diethyl-1,3-propylene bisacrylamide MDP:10-Methacryloyl oxydecyl dihydrogen phosphate CQ: Camphorquinone DMABN:Dimethylamino benzonitril BMIHP: Bis(4-methylphenyl)iodoniumhexafluorophosphate DTBHQ: di-tert.-Butylhydroquinone

Determination of pH, Viscosity, Surface Tension and Wetting Behaviour

For aqueous dental compositions 1 to 8, the pH-value, viscosity, surfacetension and wetting were determined. The pH was measured using asolvent-robust special electrode for partially aqueous systems. Theviscosity was measured using a Kinexus pro+ rotation type rheometer fromMalvern Instruments Ltd, Worcestershire, UK. The surface tension and thewetting behaviour were measured using an OCA-15E goniometer fromDataPhysics Instruments, Filderstadt, Germany, wherein SCA20 softwarefrom DataPhysics Instruments was used for measurement analysis. Thesurface tension and the wetting behaviour were measured against ambientair under exclusion of blue light.

TABLE 2 pH-value, viscosity and surface tension obtained for aqueousdental compositions 1 to 8. Aqueous dental composition: 1 2 3 4 5 6 7 8pH-Value 2.7 2.4 2.2 2.5 2.1 3.2 2.3 3.0 Viscosity 29.3  30.7  23.9 32.5  25.7  25.9  42.1  37.5  [mPa*s] Surface tension 33.7  32.6  45.9 33.0  33.2  32.7  36.5  30.5  [mN*m⁻¹]

The results listed in Table 2 show that for all aqueous dentalcompositions 1 to 8, the pH-value is less than 7, that is acidic.Furthermore, all aqueous dental compositions 1 to 8 have an advantageouslow viscosity within the range of 10 to 50 mPa*s. The surface tensionwithin a range of 30 to 50 mN*m⁻¹ is relatively low.

Furthermore, the wetting behaviour was determined on ideal moist humandentin surface prepared according to ISO 29022, and evaluated 5 secafter dosage of a droplet of the respective aqueous dental compositionon the human dentin surface. For all aqueous dental compositions 1 to 8,a full wetting was obtained, that is, the contact angle after 5 sec wasless than 3°.

Hence, owing to the specific combination of compounds of formula (I) and(V), such as BAABE and BADEP, the aqueous dental compositions 1 to 8according to the invention provide for an advantageous combination oflow viscosity, low surface tension and full wetting. This provides for asimplified application of the aqueous dental composition on a dentalsurface, while an advantageous full wetting of the dental surface isprovided.

Determination of characteristics of cured aqueous dental compositions 1to 8 The aqueous dental compositions were applied on an enamel or dentinprepared according to ISO 29022, and cured by irradiation with light.Thereafter, shear bond strength to enamel and shear bond strength todentin was measured according to ISO 29022.

TABLE 3 Shear bond strength to enamel and dentin Cured Aqueous dentalcomposition:  1  2 3 4  5  6 7  8  Shear bond 23.0 19.8 23.4 15.0 22.9strength enamel [MPa] Shear bond 35.3 23.7 32.4 31.0 28.9 strengthdentin⁴ [MPa]

The results listed in Table 2 show that particularly advantageous shearbond strength to enamel within a value range of 15 to 25 MPa and shearbond strength to dentin within a value range of 10 to 36 MPa wereobtained for the cured aqueous dental compositions 1 to 8.

1. An aqueous dental composition having a pH of at most 7, comprising:(a) 1 to 70 percent by weight based on the total weight of thecomposition of a polymerizable compound of the following formula (I):A-L-B  (I) wherein A is a group of the following formula (II)

X¹ is CO, CS, CH₂, or a group [X′Z]_(k), wherein X′ is an oxygen atom, asulfur atom or NH, Z is a straight chain or branched C₁₋₄ alkylenegroup, and k is an integer of from 1 to 10; R¹ is a hydrogen atom,—COOM, a straight chain or branched C₁₋₁₆ alkyl group which may besubstituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroarylgroup, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₃₋₆ cycloalkyl group whichmay be substituted by a C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₆₋₁₄ aryl or C₃₋₁₄heteroaryl group which may be substituted by —COOM, —PO₃M, —O—PO₃M₂ or—SO₃M, R² is a hydrogen atom, —COOM a straight chain or branched C₁₋₁₆alkyl group which may be substituted by a C₆₋₁₄ aryl or C₃₋₁₄ heteroarylgroup, —COOM, —PO₃M, —O—PO₃M₂ and —SO₃M, a C₃₋₆ cycloalkyl group whichmay be substituted by a C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, or a C₆₋₁₄ aryl orC₃₋₁₄ heteroaryl group which may be substituted by —COOM, —PO₃M,—O—PO₃M₂ and —SO₃M, L is a divalent C₂₋₁₂ alkenylene linker group, whichmay contain 1 to 3 carbonyl groups or heteroatoms selected from oxygen,nitrogen and sulfur, and which may be substituted by a hydroxyl group, aC₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, wherein M is ahydrogen atom or a metal atom; B is selected from (i) a group accordingto the definition of A, (ii) a group of the following formula (III)

X² independently has the same meaning as defined for  X¹ in formula(II), R^(1′) and R^(2′) are independent from each other andindependently have the same meaning as defined for R¹ and R² in formula(II), R is a hydrogen atom,  a straight chain or branched C₁₋₁₆ alkylgroup which may be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ arylor C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,  a C₃₋₆cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be substituted by—COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, (iii) a group of the following formula(IV)

wherein X³ is CO, —CH₂CO—, CS, or —CH₂CS—, R^(1″) and R^(2″) which areindependent from each other and independently have the same meaning asdefined for R¹ and R² in formula (II), or (iv) a group [Z′X″]_(m)E,wherein Z′ is a straight chain or branched C₁₋₄ alkylene group, X″ is anoxygen atom, a sulfur atom or NH, E is a hydrogen atom,  PO₃M₂,  astraight chain or branched C₁₋₁₆ alkyl group which may be substituted bya C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM,—PO₃M, —O—PO₃M₂ or —SO₃M,  a C₃₋₆ cycloalkyl group which may besubstituted by a C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroarylgroup, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,  a C₆₋₁₄ aryl or C₃₋₁₄heteroaryl group which may be substituted by —COOM, —PO₃M, —O—PO₃M₂ or—SO₃M, and m is an integer of from 1 to 10; and wherein M of any one R¹,R², L, R and E, which M are independent from each other, each representa hydrogen atom or a metal atom; (b) 2 to 20 percent by weight based onthe total weight of the composition of a polymerizable compound of thefollowing formula (V):A′-L′-A′   (V) wherein the A′ which are independent from each other,each represent a group of the following formula (VI)

wherein X²* independently has the same meaning as defined for X¹ informula (II), R¹* and R²* are independent from each other andindependently have the same meaning as defined for R¹ and R² in formula(II), R* is a hydrogen atom, a straight chain or branched C₁₋₁₆ alkylgroup which may be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ arylor C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₃₋₆cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be substituted by —COOM,—PO₃M, —O—PO₃M₂ or —SO₃M, L′ is a divalent C₂₋₁₂ alkylene linker group,which may contain 1 to 3 carbonyl groups or heteroatoms selected fromoxygen, nitrogen and sulfur, and which may be substituted by a hydroxylgroup, a C₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, wherein M isa hydrogen atom or a metal atom; wherein M of any one R¹*, R²*, L′ andR*, which M are independent from each other, each represent a hydrogenatom or a metal atom; (c) 1 to 20 percent by weight based on the totalweight of the composition of one or more polymerizable monomers havingone or more acidic groups; (d) 0.001 to 5 percent by weight based on thetotal weight of the composition of an initiator system; (e) 0.001 to 1percent by weight based on the total weight of the composition of astabilizer; and (f) 25 to 50 percent by weight based on the total weightof the composition of a solvent mixture comprising water and an organicsolvent; wherein the aqueous dental composition has storage stabilityfor 30 days at 50° C.
 2. The aqueous dental composition according toclaim 1, wherein B is a group according to the definition of A.
 3. Theaqueous dental composition according to claim 1 or 2, wherein X¹ informula (II) is CO.
 4. The aqueous dental composition according to claim1, wherein X² in formula (VI) is CO.
 5. The aqueous dental compositionaccording to claim 1, wherein L is —CH₂CH═CHCH₂—.
 6. The aqueous dentalcomposition according to claim 1, comprising a polymerizable phosphoricacid ester as a polymerizable monomer having one or more acidic groups.7. The aqueous dental composition according to claim 1, which furthercomprises a polymerizable monomer having at least three polymerizabledouble bonds.
 8. The aqueous dental composition according to claim 1,wherein the stabilizer is a compound of the following formula (VII)and/or (VIII):

wherein the R³, which may be the same or different, independentlyrepresent a branched C₃₋₈ alkyl or alkenyl group or a C₃₋₈ cycloalkyl orcycloalkenyl group, R⁴ represents a hydrogen atom, a C₁₋₆ alkyl or C₂₋₆alkenyl group, or a C₁₋₆ fluoroalkyl or C₂₋₆ fluoroalkenyl group, Xrepresents a group selected from a C₁₋₈ alkyl group or a C₃₋₈ cycloalkylgroup, and n is 0, 1 or
 2. 9. The aqueous dental composition accordingto claim 1, wherein the organic solvent of the solvent mixture isselected from the group consisting of ethanol, n-propanol, iso-propanol,n-butanol, iso-butanol, sec-butanol, tert-butanol, acetone and methylethyl ketone.
 10. The aqueous dental composition according to claim 1,wherein the solvent mixture comprises at least 1 percent by weight basedon the total weight of the composition, of water.
 11. The aqueous dentalcomposition according to claim 1, which further comprises a particulatefiller.
 12. The aqueous dental composition according to claim 1, whichis selected from a dental adhesive composition, a dental bonding agent,a dental primer, a dental infiltrant, a pit and fissure sealant, adental desensitizing composition, a pulp capping composition, a dentalcomposite, dental glass ionomer cement, a dental cement, a seal andprotecting composition for naked tooth necks, and a dental root canalsealer composition.
 13. A method of using a composition for thepreparation of an aqueous dental composition having a pH of at most 7;said method comprising the step of mixing the composition comprising:(a) 1 to 70 percent by weight based on the total weight of thecomposition of a polymerizable compound of the following formula (I):A-L-B  (I) wherein A is a group of the following formula (II)

X¹ is CO, CS, CH₂, or a group [X′Z]_(k), wherein X′ is an oxygen atom, asulfur atom or NH, Z is a straight chain or branched C₁₋₄ alkylenegroup, and k is an integer of from 1 to 10; R¹ is a hydrogen atom,—COOM, a straight chain or branched C₁₋₁₆ alkyl group which may besubstituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroarylgroup, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₃₋₆ cycloalkyl group whichmay be substituted by a C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₆₋₁₄ aryl or C₃₋₁₄heteroaryl group which may be substituted by —COOM, —PO₃M, —O—PO₃M₂ or—SO₃M, R² is a hydrogen atom, —COOM a straight chain or branched C₁₋₁₆alkyl group which may be substituted by a C₆₋₁₄ aryl or C₃₋₁₄ heteroarylgroup, —COOM, —PO₃M, —O—PO₃M₂ and —SO₃M, a C₃₋₆ cycloalkyl group whichmay be substituted by a C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, or a C₆₋₁₄ aryl orC₃₋₁₄ heteroaryl group which may be substituted by —COOM, —PO₃M,—O—PO₃M₂ and —SO₃M, L is a divalent C₂₋₁₂ alkenylene linker group, whichmay contain 1 to 3 carbonyl groups or heteroatoms selected from oxygen,nitrogen and sulfur, and which may be substituted by a hydroxyl group, aC₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, wherein M is ahydrogen atom or a metal atom; B is selected from (i) a group accordingto the definition of A, (ii) a group of the following formula (III)

X² independently has the same meaning as defined for  X¹ in formula(II), R^(1′) and R^(2′) are independent from each other andindependently have the same meaning as defined for R¹ and R² in formula(II), R is a hydrogen atom,  a straight chain or branched C₁₋₁₆ alkylgroup which may be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ arylor C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,  a C₃₋₆cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be substituted by—COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, (iii) a group of the following formula(IV)

wherein X³ is CO, —CH₂CO—, CS, or —CH₂CS—, R^(1″) and R^(2″) which areindependent from each other and independently have the same meaning asdefined for R¹ and R² in formula (II), or (iv) a group [Z′X″ ]_(m)E,wherein  Z′ is a straight chain or branched C₁₋₄ alkylene group,  X″ isan oxygen atom, a sulfur atom or NH,  E is a hydrogen atom,  PO₃M₂,  astraight chain or branched C₁₋₁₆ alkyl group which may be substituted bya C₃₋₆ cycloalkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM,—PO₃M, —O—PO₃M₂ or —SO₃M,  a C₃₋₆ cycloalkyl group which may besubstituted by a C₁₋₁₆ alkyl group, a C₆₋₁₄ aryl or C₃₋₁₄ heteroarylgroup, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M,  a C₆₋₁₄ aryl or C₃₋₁₄heteroaryl group which may be substituted by —COOM, —PO₃M, —O—PO₃M₂ or—SO₃M, and  m is an integer of from 1 to 10; and wherein M of any oneR¹, R², L, R and E, which M are independent from each other, eachrepresent a hydrogen atom or a metal atom; and (b) 2 to 20 percent byweight based on the total weight of the composition of a polymerizablecompound of the following formula (V):A′-L′-A′   (V) wherein the A′ which are independent from each other,each represent a group of the following formula (VI)

wherein X²* independently has the same meaning as defined for X¹ informula (II), R¹* and R²* are independent from each other andindependently have the same meaning as defined for R¹ and R² in formula(II), R* is a hydrogen atom, a straight chain or branched C₁₋₁₆ alkylgroup which may be substituted by a C₃₋₆ cycloalkyl group, a C₆₋₁₄ arylor C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, a C₃₋₆cycloalkyl group which may be substituted by a C₁₋₁₆ alkyl group, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, aC₆₋₁₄ aryl or C₃₋₁₄ heteroaryl group which may be substituted by —COOM,—PO₃M, —O—PO₃M₂ or —SO₃M, L′ is a divalent C₂₋₁₂ alkylene linker group,which may contain 1 to 3 carbonyl groups or heteroatoms selected fromoxygen, nitrogen and sulfur, and which may be substituted by a hydroxylgroup, a C₆₋₁₄ aryl group, —COOM, —PO₃M, —O—PO₃M₂ or —SO₃M, wherein M isa hydrogen atom or a metal atom; wherein M of any one R¹*, R²*, L′ andR*, which M are independent from each other, each represent a hydrogenatom or a metal atom; and (c) 0.001 to 1 percent by weight based on thetotal weight of the composition of a stabilizer; to form the aqueousdental composition having a pH of at most 7; wherein the aqueous dentalcomposition has storage stability for 30 days at 50° C.